Microcolumnar structure of Co-Cr film has been studied with use of chemical etching. Only the columns are dissolved leaving the column boundaries a microhoneycomb structure. From the composional analysis of etchant after etching, Cr segregated column boundaries have been confirmed to exist even in the high rate sputtered Co-Cr films. The Co-Cr film with higher Hc shows sharper and narrower grain boundaries whose Cr content is also higher. It is concluded that degree of Cr segregation is very important factor for the control of the mametic oronerties of the Co-Cr films.
Magnetic thin films of Fe1-xCrx (x=0.33 to 0.40) with perpendicular magnetization were obtained using the rf sputtering method for the first time. Fe66Cr34 deposited onto unheated substrate had Ku 6 × 105 erg/cm3, Ms 280 emu/cm3 and Hc⊥ 700 Oe. Film composition and substrate temperature during film preparation were the most important factors inducing perpendicular anisotropy. X-ray diffraction studies showed that the induction of perpendicular anisotropy was always accompanied by growth of the crystalline phase (Cr-dominan bcc phase). FeCr films also exhibited high corrosion resistivity in an oxidative environment. FeCr is a potential material for perpendicular magnetic recording.
Electrical resistivity (ρ) of reactive RF sputtered CO-CoO films increases and the temperature coefficient of resistivity (TCR) decreases with the formation of CoO. For films of which saturation magnetization (Ms) is more than 670 emu/cm3, ρ decreases irreversibly above 370 K by deoxidization. For films of which Ms is less than 470 emu/cm3, ρ increases irreversibly above 420K. After the irreversible increase of ρ, coercivity (Hc) and rectangular ratio of hysteresis loop perpendicular to the film plane increase, and Hc parallel to the film plane decreases.
Several experimental studies recently have been carried out on magnetic properties for Nd-Fe-B alloys. In this paper, we report on the effects of partial substitution of cobalt for iron in the Nd-Fe-B system. The samples prepared by powder metallurgical method have composition Nd23-yFe77-2xCo2xBy, where x=0∼10, y = 5∼10. we have obtained significant improvement in the Curie temperature with increasing cobalt content in the alloy system. The temperature coefficient of σr of the Nd16Fe66Co11B7 is about -0.02%/°C, in the temperature range 20∼100°C compared with -0.03%/°C for the Nd-Fe-B samples. We have achieved a magnt with the maximum energy product of 41 MGOe in the Nd-Fe-Co-B system.
The read spacing losses in perpendicular magnetic recording have been investigated experimentally for various combinations of heads and media. The spacing loss coefficient, K, which is the slope when the spacing loss is plotted versus d/λ, has been measured for sinusoidal magnetization. The results show that for a single layer medium, K is almost the same as that in longitudinal recording, and that for a double layer medium, the K value is large at long wavelengths and becomes small with decreasing wavelength to the value less than 54.6. Particularly for a ring head, a striking wavelength dependence of K is observed. Such a wavelength dependence results from the change of the distribution and the magnitude of the head sensitivity function with spacing. Nevertheless in digital recording, the deterioration in recording density characteristics with increasing spacing is small, even at low densities, because of the contribution of harmonics in output singnals.
The domain structures of narrow track single pole heads for perpendicular magnetic recording have been observed and their effects on the reproducing sensitivities are investigated. The ratio of the double height 2h of the closure domain to the track width W increases when the track width and the anisotropy field Hk of a Co-Zr-Nb amorphous main pole film decrease. The maximum reproducing sensitivity for each narrow track head is obtained for the optimum value of Hk, when the ratio of 2h to W is about 30%. When the Hk is smaller than the optimum value giving the maximum sensitivity, the reproduced voltage not only decreases but also changes with every cycle of recording. On the other hand, the reproduced voltage does not change and becomes smaller for larger Hk, because the permeability of the film decreases. The reproducing sensitivity of the narrow track single pole head, made of the film having the optimum Hk, does not decrease even for the head of 10 μm wide track.
Electroless plated Co-Ni-Re-P alloy films for perpendicular recording medium were investigated and developed. It was found that the addition of tartronic acid into the plating bath makes it possible to form the Co-Ni-Re-P perpendicular anisotropy films with noMnSO4 present. The Co-Ni-Re-P alloy film whose composition is simpler than that of the previously developed Co-Ni-Re-Mn-P films, has a higher potential than that of Co-Ni- Re-Mn-P alloy film from a practical use viewpoint as a perpendicular recording media. Readlwrite characteristics of 8 inch disks using Co-Ni-Re-P medium were also obtained and measured with a combination of a ring head. Characteristics whose quality was almost equal to those of Mn codeposited media were obtained, and a higher recording density would be expected with improvement in the matching condition between head and disk properties. The recording density of 54 kFRPI as D50 was obtained with 0.02 μm thick magnetic medium using a 0.33 μm gap length ring head at 0.12 μm head-medium spacing.
A single pole type thin film head for perpendicular magnetic recording was developed, and the effects of head and disk parameters were studied. The newly developed single pole head consists of an amorphous Co-Zr main pole and a coil of 16 turns. The pole is tapered at the tip end, ranging from 0.2 μm to 0.5 μm in thickness and from 2 μm to 15 μm in depth. First, the effects of the pole thickness and pole depth on write and read performance of the head were investigated. A CO-Cr/permalloy double layer rigid disk was used for evaluation. The thickness of the CO-Cr layer is 0.14 μm, and that of the permalloy underlayer is 0.5 μm. Perpendicular coercivity of the CO-Cr layer is 730 Oe. Recording density increased as the pole thickness decreased, and a D50 of 70 kFRPI was achieved for a head with a 0.2μm pole thickness. Isolated output was 0.53μVp-p/μm/turn at a disk speed of 6 m/s. Magneto-motive force for saturation recording was as low as 0.19 AT. It was found that the influence of the pole depth on the write and read performance is very little. Next, the effects of perpendicular coercivity and film thickness of the double layer disk on the recording characteristics were examined. Recording density and write sensitivity were improved as the thickness of the Co-Cr layer decreased. Output voltage increased with the perpendicular coercivity.
Rare earth-transition metal amorphous films are promising for erasable optical memory media. However, they have the drawback of poor reliability due to the poor corrosion resistance. The corrosion of the films is classified as being surface oxidation, selective oxidation of RE metals, and pitting corrosion. We have studied the corrosion behavior and succeeded in improving the corrosion resistance. To improve corrosion resistance, one of the elements, Co, Ni, Pt, Al, Cr, and Ti, is added to Tb-Fe and Tb-Co films by simultaneous sputtering. The films (no protection) are subjected to an accelerated aging test. The elements are classified into two groups: (Co, Ni, and Pt) and (Al, Cr, and Ti). The former group elements are only effective in preventing surface oxidation and pitting corrosion. The latter group elements, however, are effective in inhibiting corrosion of all the above modes. This high corrosion resistance can be explained in terms of to their ability to getter oxygen and to form passive states. The degree of these effects, in order of strength, is Cr Ti Al. These additives cause no appreciable change in the magnetooptical properties.
The reliability of rare earth-transition metal (RE-TM) alloy films with a multilayer structure which attains a high signal to noise ratio is discussed. In order to study the stability of the multi-layer magneto-optic (M-O) medium which consists of the GdTbFe layer sandwiched between nitride layers, heating tests (380∼480°C) have been conducted. Magneto-optic properties are evaluated by Kerr hysteresis loop. In a high temperature environmemt (400°C), the coercive force (Hc) is found to increase and the the Curie temperature (Tc) is found to decrease. It seems that the change of Hc and Tc results from the decrease of effective RE component. However the sample using SUS-304 as a reflector exhibits less change of Hc than that using Al at 4OO°C, and the sample heated in the vaccum (2×10-6 torr) exhibits a small change in Hc. From these results, it is felt that the phenomenon in a high temperature environment is caused by selective oxidation of RE atoms. There is little change of magneto-optic properties at 380°C. Therefore the multilayer M-O medium using AIN is promising as a high stability material for thermo-magnetic recording.
A new method is proposed for checking the magnetic anisotropy of rare earth-transition metal amorphous alloy films for thermomagnetic recording. The Hall loop is measured when the magnetic field H is applid to the film with inclination angle α (being measured relative to the film normal), and the relationship between the loop coercivity Hc′ and γ, the orientation angle of H in the film plane, is plotted in polar coordinates. According to the theoretical consideration, if the film has the oblique magnetic anisotropy then the shape of the Hc′-γ plot is elliptical. Therefore, if the measured Hc′-γ plot fits this elliptical law then the direction of the magnetic easy axis of the film can be calculated using the equations presented in this paper.
It has been found that the magneto-optic properties of rare earth-transition metal (RE-TM) amorphous thin films, which are used as magneto-optical memory media, can be enhanced by a multilayered structure using the interference of light. The apparent refractive index of the substrate can be varied by coating the appropriate dielectric layer which has an optical thickness of 1/4 of the laser wavelength λ. By inserting this λ/4-layer between the substrate and the conventional dielectric layer for Kerr enhancement/RE-TM layer/reflector-structure, figure of merit √Rθk (θk: Kerr rotation, R: reflectivity) can be improved by 6∼7 dB for R≥0.1 compared to a simple substrate/RE-TM layer-structure. This figure of merit is almost the same as the one previously reported for a substrate/RE-TM layer/dielectric layerlreflector-structure. However, since the thickness of the RE-TM layer of the former structure is larger than that of the latter, it is considered to be more suitable as a recording medium taking reliability into account.
Optical disk memory using amorphous rare-earth-transition-metal (RE-TM) films have been developed for erasable optical disks for applications of high density, large volume data storage. In order that the film can be used in applications, it is necessary to improve its reliability. The key factors in improving the reliability of these disks are reduction of the RE-TM film oxidation and improvement of heat-resistance property of organic substrate. Tb-Co film forming on the epoxy-resin substrate with adequate sputtering conditions protects against oxidation and shows good magneto-optical properties. In addition, the epoxy-resin substrate has small birefringence-retardation and a smooth groove shape fabricated by means of an Omega-casting method. These results demonstrate that the optical disk with Tb-Co on epoxy substrate is suitable media for erasable disks for practical applications.
An investigation was made to evaluate the variation in the magnetic and magneto-optic properties of amorphous TbFeCo alloy films deposited by the two source magnetron-sputtering method as a function of sputtering parameters, such as rf input power, Ar pressure and substrate rotation. With the variation of Ar pressure, saturation magnetization (Ms), coercivity (Hc) and deposition rate of amorphous TbFeCo alloy films changed. Ms reached the minimum value, although Hc and the deposition rate reached the maximum value at about 5mTorr Ar. Using mass spectrometry to detect the ionic species in the glow discharge plasma, we found that the ion current for ionic species, such as Ar+, Fe+, Co+ and Tb+, had the maximum value at about 5 mTorr Ar. These results indicate that the changes in the magnitude of Ms, Hc and deposition rate are due to the changes in sputtered atomic number. With the variation of substrate rotation, Ms, the perpendicular magnetic anisotropy energy (K⊥) and the Kerr rotation angle (θk) did not change above about 20 rpm but increased rapidly below this. This seems to be due to the changes of composition and structure in the micro area of the film; however, these were not detected by energy dispersive X-ray fluorescence analysis, Auger electron spectroscopy or reflection electron diffraction.
GdFe and TbFe films sputtered with substrate bias voltage (VB) have been annealed both in air and in vacuum at temperatures up to 300°C In the case of annealing in air the oxidation occurs at the film surface and forms an oxidized layer that has in-plane magnetization,and therefore, the perpendicular anisotropy (Ku) decreases. Crystallographic structure of the films changes from the amorphous state into crystal-like one with increasing VB. The amorphous films sputtered with low VB oxidize more readily than the crystal-like films. Consequently the films sputtered with low VB show a larger decrease in Ku than those with high VB. Annealing in vacuum does not seem to change the film properties.
Crystal stractures and magnetic properties have been studied for magnetic oxde films prepared by a bias sputtering using garnet targets deposited on SiO2, GGG and sapphire substrates. The sputtered films were amorphous and those annealed at 700°C where crystallized. The films, which were sputtered at zero bias, were poly-crystalline garnet structures on any substrates. When bias voltage was applied during sputtering, singlecrystalline garnet films were formed on GGG substrates and oriented orthoferrite films were grown on sapphire substrates.
Single crystals of highly Bi-substituted gadolinium iron garnets have been grown by an improved flux method in which Bi2O3, is used as a flux. Faraday rotation and optical absorption are measured in the near-infrared region at room temperature. The magnetooptical figure of merit is 44deg/dB at 0.78μm in Gd1.8Bi1.2Fe5O12. A very compact optical isolator has been developed for 0.8μm wavelength by using this crystal as a Faraday rotator. The optical isolator features 1.5dB insertion loss and 32 dB backward loss at wavelength of 0.78μm.
High-quality films of (BiNdLu)3(FeAlLu)5O12 and (BiGd)3(FeAl)5O12 have been grown by means of LPE. We found that Bi garnet films with the absorption loss of 300∼400dB/cm at wavelength 0.8μm can be prepared by this technique with use of PbO-B2O3-Bi2O3, fluxed melts. The magneto-optical figure of merit of (BiGdLu)(FeAlLu)5O12 films reached about 10 deg/dB at 0.8 μm for as-grown films and 14 deg/dB for chemically reduced films in aqueous FeCl2 solution. Films of (BiGd)3(FeAl)5O12 of thickness greater than 100μm and a figure of merit of 9 deg/dB are successfully grown onto NdGG and Ca, Mg and Zr substituted GGG substrates. From the temperature dependence of Faraday rotation angle of the film, it is found that the Curie temperature is 300°C and the compensation temperature, -98°C An optical isolator for a wavelength region of 0.8μm is constructed by using the thick film which have the perpendicular and low saturation magnetization (4πMs=603 G). The forward loss of the isolator is found to be 6.3dB and the backward loss, 24 dB.
Thin films with the composition of Co0.8Cr1.2Fe1.0O4 have been rf sputter-deposited at Ts (substrate temperature)=250∼590°C on substrates of quartz glass, SiO2-coated stainless steel, and aluminum. They were polycrystalline with spinel structure. When 350°C<Ts< 500°C the films exhibited no preferred orientation, while, when Ts>55O°C, they exhibited <111> orientation perpendicular to the film plane. The film deposited on quartz glass had magnetic easy direction parallel to the film plane, while those deposited on stainless steel and aluminum had magnetic easy direction perpendicular to the film plane. This anisotropy may be caused by the internal stress introduced by the difference between the thermal expansion coefficients of the film (αf) and the substrate (αs): The films deposited on stainless steel and aluminum have a compressive stress because of αs>αf, which results in perpendicular magnetic anisotropy via positive magnetostriction of the film. For the film deposited on stainless steel, the apparent polar Kerr rotation angle including the enhancement by optical interference at SiO2-underlayer reached as high as 3° at λ=740 nm. This film may be a promising material for magneto-optic memory.
The magneto-optical properties of iron oxide (FeOx) films prepared by reactive ionized cluster beam (R-ICB) technique have been studied by the measurement of Faraday rotation angle (θF). Preparation of FeOx films was made by the deposition of Fe clusters onto a glass substrate under an oxygen pressure 2 ×10-4Torr. In this study, Fe clusters and oxygen partially were ionized and accelerated. The value of θF in the visible and near infrared region remarkably increased with increasing acceleration voltage (Va), which is considered due to Fe+ ions in FeOx films. Also, the Faraday rotation loop in the field perpendicular to the film plane at 632.82 nm showed hysteretic phenomena for a certain value of which is related to the promotion of <111> orientation in the Fe3O4 phase. These results indicate that kinetic energies of Fe clusters and oxygen act effectively on the formation of FeOx films of different composition (x), and that the magneto-optical properties of prepared films are controlled by adjusting theacceleration voltage.
The optical and magnetooptical properties of Cd1-xMnxTe films prepared by ionized cluster beam (ICB) deposition technique have been studied. Preparation of these films was made by a simultaneous deposition of CdTe and MnTe clusters. Films with the <111> axis preferential orientation were obtained on glass substrates, and epitaxial films were grown on sapphire substrates. The optical band gap was found to increase from 1.5eV to 2.6eV with the increase of composition x, which was controlled by the acceleration voltage. A large dispersion of Faraday rotation was observed near the band gap energy, and the position shifted toward higher photon energy with increasing composition x. The dispersion curve was related to the absorption spectrum near the band gap energy. For the epitaxial film, the value of the Faraday rotation (θFmax= -3.61 × 103deg./cm at H=5kOe) was about two times greater than that for the film deposited on a glass substrate.
Thin films of Ptx(MnSb)1-x have been prepared by a rf-sputtering, and have investigated as a new material for magneto-optic applications. Room temperature saturation magnetization (Ms) and coercive force (Hc) for as-sputtered and annealed films are measured using a vibrating sample magnetometer (VSM). The easy axis of magnetization exists in the plane for all films, and the values of Ms and Hc vary with the concentration of Pt in PtMnSb films. Measurements of polar Kerr rotation θk are performed at a He-Ne laser wavelength (632.8 nm). For the film at x ≅ 0.15, annealed at 500°C for 10 hours in a vacuum, the polar Kerr rotation is found to be 0.9° when an external DC magnetic field 4 kOe is applied in a perpendicular diredtion.
The temperature dependence of Young's modulus of transition metal-metalloid amorphous alloys, (Fe1-xM)85B15 (M: Cr, Mn, Co, Ni), (Fe1-xMx)77Si10B13 (M: Co, Ni), Fe-B, Fe-P, Co-B, has been measured by a pulse echo delay-line technique in the temperature range from R.T. to 600°C. Young's modulus Es measured under the saturation of magnetization for Mn and Cr containing alloys shows softening below Tc because of the magnetovolume effect. The contribution of the magnetovolume effect to Young's modulus is quantitatively analysed and its dependence on the electron number per transition metal atoms neff is presented. The magnetovolume contribution to Young's modulus passes through a maximum at neff∼8.0 and smears above neff∼8.3. These results are discussed in connection with the anomalous stress dependence of the magnetovolume coupling constant in the transition metal-metalloid amorphous alloys.
The temperature dependence of initial permeability has been measured in the temperature range from 4.2K to Curie temperature for amorphous (Fe1-xNix)77Si10B13 (x≥0.8) alloys. Anomalous peaks (1∼3 peaks) are observed in μ-T curves near the Curie temperature. The change of the peaks with increasing driving magnetic field has been examined for x=0.8 and 0.9 alloys. Based on these results, the anomalous peaks can be explained in terms of the natural magnetic resonance in addition to the Hopkinson peak.
Amorphous magnetostrictive wires manufactured by UNITIKA Co. induce sharp and stable voltage pulses against ac fields of more than 0.1 Oe at the frequencies 0.01 Hz-10 kHz, and are suitable for application to pulse generator elements for rotary encoders and magnetic-type security sensors. In this paper, the sensitive, highly stable large Barkhausen effect and Matteucci effect in these amorphous wires are analyzed using a domain-wall propagation model. Theoretical values are compared with the experimental results for the voltage pulse generation characteristics at the pick-up windings and between both ends of the amorphous wires. Effects of applications of tensile and torsional stresses and annealing on these pulse generations are also investigated. The Matteucci voltage increased about to 20 times and about to 6 times due to twisting and annealing under twisting, respectively.
Magnetic permeability and its thermal stability have been investigated in low magnetostrictive amorphous Fe-based alloys. Crystallization temperature, Curie temperature, saturation magnetization, and effective permeability up to 1 MHz have been measured. A value for the effective permeability of 2×104 is obtained at 1 kHz for Fe-based amorphous alloys with low magnetostriction of the 10-6 order, which is comparable to the value of zero magnetostrictive Co-based amorphous alloys. Disaccommodation and thermal variation of magnetic permeability have been also measured. Small disaccommodation, good thermal stability, are achieved in low magnetostrictive Fe-based amorphous alloys. Disaccommodation, however, is not directly proportional to λs2 in the 10-6 range of magnetostriction, suggesting that the magnetostrictive model of Allia is not valid in low magnetostrictive Fe-based amorphous alloys. Even for Fe-based amorphous alloys, disaccommodation should be considered in terms of induced magnetic anisotropy, in addition to the magnetostriction.
The amorphous phase region is located in a narrow area near the side of CaO-SiO2. The magnetization of amorphous oxides is very small at the room temperature, but markedly increases for temperatures lower than about 50 K. The room temperature Mössbauer spectra indicate paramagnetic peaks. The spectra at 77K reveal six weak Zeeman peaks buried in the background. At 4.2 K, a well resolved hyperfine sextet is observed. The Mössbauer results suggest that the Fe atoms are distributed inhomogeneously in the solid and that the structural short-range order around Fe atoms is very strong, having random bonding and distance fluctuation.
Stripe domin head dynamics for a strong drive field in a current stretcher bubble detector have been studied for three different component garnet films with different dynamic properties. It has been observed that the stripe head velocity is sometimes very small in the beginning of stretching in a hard bubble suppressed region and that there are two streching modes with fast rise and slow rise times in an unimplanted stretching region. The stripe head mobilities in the fast rise mode are approximately 1/3 the plane wall mobilities. The mobilities in the slow rise mode are mostly proportional to Gilbert’s damping parameters. These two modes are discussed as originating from vertical Bloch lines at the stripe head by using Slonczewski’s velocity equation for a adomain wall with Bloch lines. Saturation velocities obtained for two modes are 42 m/s, which is nearly equal to plane wall peak velocity.
In ion-implanted and Permalloy hybrid bubble memory devices, the operating bias field region of ion-implanted tracks is lower than that of Permalloy tracks when the cell size is less than 4μm × 4μm. This reduces the overall bias field margin. The operating bias field region of Permalloy tracks has been shifted using the garnet film thickness dependence of a bubble collapse field. Thickness of a garnet film under Permalloy tracks is reduced using the ion-milling technique. The ion-milled region has a low coercive field and shows a good bias field margin. It has been confirmed in hybrid bubble memory devices with a 3.5μm × 3.5μm cell size that the operating bias field adjustment made by thinning a garnet film can improve the overall bias field margin.
A formulation has been developed in which the magnetization structure along a magnetic domain wall within a vertical Bloch line is regarded as packed into a single point on the wall, concentrated Bloch-line point. Equations of motion have been derived for the concentrated Bloch line from equations of wall motion developed previously for a two-dimensional wall which was regarded as a locus of domain-center points. Programs have been developed to solve the motion of a domain wall which is arbitrary in shape and contains arbitrary number of concentrated Bloch lines. The results of computer simulation made for bubbles and plane-like walls show the validity of the formulation and the numerical method. The new equations of motion for concentrated Bloch line have been found not to be as stiff as the conventional equations of wall motion in the case with Bloch lines. An outline of the formulation and the method of numerical solution are presented together with preliminary results of computer simulation.
Fe-Al alloy films have been obtained by rf sputtering technique and have been investi. gated by means of X-ray diffraction, magnetization and Mössbauer effect measurements A well disordered bcc phase is extended up to about 70at % Al, an amorphous phase between 75 and 85at % Al and an fcc phase from 90 to 100at % Al. The disordered bcc alloys are ferromagnetic at low temperatures and show a perpendicular magnetic anisotropy at 290 K for about 38 at % Al. The amorphous and fcc alloys are paramagnetic even at 4.2 K.
Magnetoresistive effect and anisotropy field of Ni-Co films deposited under orthogonal switching field were studied. The magnetoresistive effect was maximum for 77 Ni-Co films. The anisotrophy fields were 0.4-0.7 kA/m for these films. Demagetization field, domain structure and magnetization process were investigated for the composite Ni-Co/ Ni-Fe film of a striped configuration. When had thick Ni-Fe films are placed near the Ni-Co films, the demagnetization field were small, domain walls were short and magnetization processes were homogeneous.
High resolution deflection patterns of 200 kV transmission electron microscopy are presented demonstrating different structures of 180° walls in epitaxially grown (100) iron films and magnetostatically coupled layered films of polycrystalline iron. In (100) iron films the structure of the 180° wall becomes more asymmetric not only across the wall thickness but also in the other two directions as the film thickness increases from 500 to 3000Å. When all the dimensions of crystalline grain, film thickness and wall thickness are 2000-3000Å. the 180° walls have fine structures which are modulated mainly by the grain. In layered films less than 550Å in each dimention, the two coupled 180° walls frequently change between overlap-position and split-position, and the period of such shift varies from several μm to a few thousand angstroms depending on the film structure.
Propagation properties of fundamental magnetoelastic waves (MEWs) in a highly magnetostrictive slab have been studied. Analysis and experiment show that there exist three fundamental MEWs: Lamb extensional-type, Lamb flexural-type and SH-type MEWseven in a single homogeneous magnetic slab. The results reveal that the propagation properties of MEWs are determined by not only the magnetic parameters such as the magnetoelastic coupling constant but also by the geometrical ratio of the thickness to the drive frequency. The analysis suggests that in order to realize large velocity change in MEWs with a small field the easy axis direction should be changed according to whether the Lamb-type or the SH-type MEW is used. The SH-type MEW exhibits distinct frequency dispersion which is not observed in the elastic SH-wave in a non-magnetic slab.
The propagation of magnetic surface-acoustic-waves (MSAW) are presented on rf-sputtered amorphous Fe-Co-B films deposited on glass substrates. Piézoelectric transducers employing IDT and Al-doped ZnO films were used for excitation and detection of MSAW. Three dominant waves appear in this configuration−two Lamb type waves of (P+SV)-extensional mode and (P+SV)-flexual mode as well as Love (SH) type waves, among which the SH-type waves were the most intensively excited. MSAW were subjected to change by magnetic annealing in a field applied parallel to the sample width. The controllable change in the sound velocity with field reaches as high as 7.7% at 30MHz operation in SH-type waves. This value is several hundred times larger than those reported so far. SH-type waves undergo a marked attenuation depending on field. This is interpreted as follows: The MSAW energy is dissipated mostly in the form of microeddy current loss in metallic films. The dissipation takes place more distinctly in SH-type waves, because these waves propagate concentratedly in the magnetic conductive overlay.
Amorphous Co-Ti films have been prepared by sputtering technique. Anisotropy dispersion and domain structures have been investigated. Co-Ti films are annealed in a static (DFA) or a rotating (RFA) field. By DFA, it is possible to induce the anisotropy. In Co83Ti17 DFA films of 1 μm thickness, the anisotropy is induced to 8 Oe. Half width of magnitude dispersion of the distributed curve is ±0.6 Oe while the angular dispersion is several degrees. By RFA, the anisotropy can be reduced, and its easy axis is widely distributed to cover almost 360°. Considering dispersion, the difference between the initial permeability calculated by the anisotropy measured macroscopically and the measured one seems difficult to explain.
Recently, CoZrNb amorphous metal films have been studied for use in perpendicular magnetic recording heads, because of their high saturation magnetization, high permeability and small magnetostriction coefficient. In this paper, the magnetic characteristics of these films are discussed as to the influence of substrates surface smoothness and the annealing effect of the amorphous films. The CoZrNb amorphous metal films are deposited on glass or ceramic substrates by the RF sputtering method. The ceramic substrates have been ground and mirror polished. The direction and amplitude of anisotropy fields (Hk) of the films on ceramic substrates are highly dependent on the grinding direction. The films are annealed within a rotating magnetic field at an appropriate temperature. Amplitudes of the Hk decrease with the annealing time. Hk direction of the films, however, is oriented along that of the applied static magnetic fields within which the films are annealed. Combining those two annealing methods, the first within a static field and the second within a rotating field, the direction and amplitude of Hk can be controlled independently to a desirable value with a small coercive force.
Magnetite (Fe3O4) thin films were prepared by RF reactive sputtering in an argon-oxygen mixed atmosphere. RF power density and total gas pressure, which affect the kinetic energy of sputtered atoms, were held constant.  preferential orientation of Fe3O4 films was improved by an increase of gas flow rate and a decrease of intermittent deposition rate. Squareness ratio (Mr/Ms) increased and coercive force (Hc) decreased with an improvement in the preferential orientation for these films.
The influence of stress on the coercivity of Fe3O4-γFe2O3 intermediary films has been studied. In order to induce various stresses, intermediary films were prepared on various kinds of substrates which had different thermal expansion coefficients. The surfaces of the substrates were coated with an SiO2 layer prior to the film preparation in order to eliminate the difference in their chemical properties. The magnetic properties and plane distances of the Fe3O4-γFe2O3 intermediary films were measured. Films prepared on the substrates having smaller thermal expansion coefficients showed larger coercivity increases. A remarkable increase in coercivity was obtained only when the stress in the film was in tension.
Losses of grain-oriented 3% silicon steel (G.O.) with orientation near (110) have been measured in order to investigate the lower limit of loss in a polycrystalline lamination steel. Highly oriented G.O. (B8≈1.98T, 60×300×0.30mm) are made by recrystallization under a temperature gradient, then thinned by chemical etching to the desired thickness. Losses of G.O. with a thickness of 0.15mm are very low, i.e., W13/50≈0.2 watts/kg, W17/50≈0.4 watts/kg. This relatively low loss is comparable to that of an amorphous magnetic material. But glass-film formation on G.O. cause an increase in loss of about 0.1 watts/kg in W17/50. Dynamic behavior of magnetic domain walls of G.O. magnetized at 60Hz is performed by the line-sampling stroboscopic technique using a 200 kV scanning electron microscope. Uniform displacemet of domain wall is observed in highly oriented G.O.
The magnetic stray field generated from domains and Bloch walls of 3% Si-Fe sheets have been measured precisely and automatically by using a Hall sensor and an averaging device connected to a personal computer. The results show that the strength of the field normal to the grain surface depend strongly on the main 180°domain width and the grain orientation, which can be explained by the theoretical analysis considering the magnetostatic interaction of the sheet. The Bloch wall mappings estimated from the measurements of stray field distributions for single crystal sheets and highly grain oriented sheets (Hi-B) are in good agreement with the practical arrangement observed by means of a colloid displaying device. Furthermore, the influences of thickness, demagnetization frequency, scratching and lamination, as the factors affecting on the stray field, are discussed.
The magnetic fields in single sheet testers are quantitatively investigated in order to develope an improved tester. The effects of quarity and thickness of the specimen, the stacking method of yoke and the air gap between specimen and yoke on the accuracy of the H coil method and the IEC method are analysed. The results obtained can be summarized as follows: (1) The error of magnetic field strength is increased when the permeability and the thickness of specimen, and the gap width between the specimen and the yoke are increased. (2) The stacking methods of yoke give a small influence on the accuracy of magnetic field strength. (3) The accuracy of magnetic field strength measured by the H coil method is 10 times better than that by the IEC method.
A new type of inverter system -Hybrid inverter system- is proposed. This system is constructed with a three-phase inverter and a magnetic frequency multiplier. The advantages of the hybrid inverter system are as follows: (1) The frequency limit of the inverter can be magnified with only a small increase in cost. (2) A filter circuit is not needed because the waveform of the output voltage is comparatively good. In this paper the operation of Hybrid inverter system is analyzed with the harmonic balance method by taking into account the characteristics of Nonlinear Zero-Phase-Sequence circuit. Guidelines for designing the system are obtained from the results of the analysis.
The characteristics of a magnetic frequency tripler with connecting filter on the primary side are presented. In carrying out the analysis, mode analysis for the tripler circuit and vector analysis for the whole system including the filter have been applied. From the results of the numerical analysis, the optimum conditions for stabilizing output power and reducing the self capacity of the system are obtained. As a consequence it is found that input current maveform and input power factor can be also improved. The results of the analysis are in good agreement with experiment, thus demonstrating that this analytical technique is useful for designing the tripler system.
New con-contact type linear displacement (oscillation) sensors are presented which combine a two amorphous-wire core multivibrator bridge with a small magnet. The nonlinearity of the relationship between magnetic field from the magnet and the distance between the detection point and the magnet is cancelled by utilizing the saturation characteristics of the amorphous-core magnetometer. Linear ranges as large as 8mm have been obtained using a zero-magnetostrictive amorphous wire (made by UNITIKA Co.) of 44mm in diameter on which two 20mm long coils are placed separately. The cut-off frequency is about 4 kHz in the displacement sensor, and the minimum detectable displacement is about 1 μm. A new sensing technique is developed using these non-contact linear displacement sensors for mechanocardiography for cardio-function diagnosis combined with the electrocardiograph.
This paper describes the fundamental operation of the orthogonal-flux type transformer for DC-AC interconnection systems. The power conversion of the orthogonal-flux type transformer is calculated by using the flux-MMF relationships of the orthogonal core, and the calculated values agree well with the experimenal ones. The analytical results obtained here are useful for designing an DC-AC interconnection system which incorporates the orthoeonal-flux type transformer.
This paper presents a numerical method for analyzing the electromagnetic transients in three phase transformer circuits, and shows numerical and experimental results of two type three phase circuits. The one circuit consists of the E-type wound core, and the other consists of three C-type wound cores. Both circuits are driven in the star-star connection. Inrush current, induced voltage and neutral voltage of transformers are investigated numerically and experimentally under the condition of zero make on phase. Observed transients are predicited by numerical simulations using this method, and the results are compared with the experimental results showing satisfactory agreement.
The miniaturization of magnetic cores wound by copper wire is difficult because of the structure. In this paper the authors describe a miniaturized inductor containing amorphous magnetic wire which they have succeeded in realizing with a large inductance per unit volume. Further, the size of the inductor is smaller than that of inductors with conventional cores. The frequency characteristics of inductance of the wire inductor is controlled by the demagnetizing factor of the amorphous wire, and one thus can realize an inductor which operates in sub-MHz frequency domain.
A micro-computer controlled high-precision system for measuring of the static hysteresis characteristics has been constructed. This systerm can be used to measure the hysteresis losses in new high permeability materials such as amorphous ribbons. In such materials the induced flux voltage waveforms consist of very sharp and large Barkhausen noises, and a considerable amount of error can be introduced in the loss measurement when the bandwidth of the flux voltage integrating system of is not suffisiently wide. The digital integrating system using a V-f converter, provides a bandwidth suffisient for measuring with high-precision the hysteresis losses in new high permeability materials.
A new circuit element with coaxial structure is proposed which is constructed by using two magnetic pipes. In this element, the inner pipe and the outer pipe are connected in series electrically, and current flows through both pipes. The element exhibits a number of interesting operating characteristics. There is a remarkable skin effect at the commercial frequency and appearance of unbalanced impedance between inner and outer pipe. In this paper, the magnetic coaxial pipe is shown to be useful as a heating element of pipe transportation for high viscous liquid by utilizing its remarkable skin effect. The voltage drop on the outside of outer pipe is very small, because the impedance of outer pipe is much smaller than that of the inner pipe. A pipe heating system with high power factor and sufficient heat generation therefore can be constructed with the magnetic coaxial pipe.