MP Test tape having as almost high reproduction characteristics as ME tape was made for high density recording with very fine metal particles of which average particle length is 0.175 μm and average axial ratio is 9 with high dispersion and longitudinal orientation technologies. Basically these technologies are conventional. However this test tape has superior characteristics suitable for ultra high density recording; its surface roughness is 3.63 nm (Rrms) and its squareness ratio is 0.89. Reproduction characteristics of it is also superior: output level is only 1.5 dB lower than ME tape at 100 kFRPI. In this paper, we describe recording density characteristics of this test tape, and show effect of improving squareness ratio and surface roughness in high density and effect of using different Bs of head on these characteristics.
In order to improve the dual layer structure in the LIPS tape preparation, i.e. more perpendicular surface layer and more longitudinal inside layer, an infrared radiation was added in the “surface air dry” stage under a perpendicular holding field. An attained tape shows higher reproduction output both in short and long wavelengths in comparison with our former tape with oblique orientation in full thickness. The dual layer tape shows a 5 dB higher reproduction output than a longitudinal tape at λ = 0.7 μm. Small aspect ratio (∼5) particle proved to be suitable for perpendicular tape because of its resistivity against calendering redisorientation. This effect is confirmed from SQRz measurement.
Perpendicularly and longitudinally oriented (PO and LO) tapes were prepared from spinel rich barium ferrite pigments with different coercivity (Hc). SFD and SFDr for LO tapes were much smaller than those for the metal particulate (MP) tape. Their outputs were measured on a drum tester using a sendust sputtered sheet laminated head. In low recording density rigion, the LO tapes showed greater output than the PO tapes. However, in high recording density region, the PO tapes showed about 3dB greater outputs than the LO tapes with almost the same Hc values in the oriented direction. D50 of the LO tape was greater than that of MP tape for almost the same longitudinal Hc value.
This work reports the effect of thinner Cr underlayer in the longitudinal metal medium that consists of Co-alloy on a Cr underlayer. The medium with thinner Cr underlayer exhibits improved signal-tonoise characteristics compared to the thicker Cr underlayer. This depends on the result that saturation magnetic flux density Bs and squareness S increased, and noise N decreased. We think that the change of saturation magnetic flux density Bs is influenced from the level of diffusion between Cr underlayer and Co-alloy film layer, that the change of squareness S is influenced from the change of Co-crystalline orientation, and that the change of noise N is influenced from the change of grain size.
Investigated is the effect of substrate temperature and substrate thickness on magnetic properties and microstructure of vacuum deposited Co-Cr films. The microstructure of the films is so much dependent on substrate temperature that columnar structure disappears with the temperature rising up to 290°C from 250°C. The disappearance deteriorates the recording characteristics of the films. The substrate thickness dependence of magnetic properties of the films is small, and this result is consistent with the simulation of thickness dependence of substrate temperature during deposition.
The effct of morphology of substrates was studied on perpendicular anisotropy Co-Cr films. Co-Cr layers were deposited on Al-3 wt%Cu underlayers with a thickness of 1.5∼40 nm which were deposited at the substrate temperature of 25∼300°C, According to SEM photographs, island structure was observed for Al-Cu films deposited at 300°C, while flat surface was observed for those deposited at 25°C. Δθ50 and Hkeff of Co-Cr films on Al-Cu underlayers deposited at 300°C were about 15° and 2 kOe, respectively, while those on Al-Cu underlayers deposited at 25°C were under 10° and about 3 kOe, respectively. The morphology of Al-Cu underlyers greatly influenced the perpendicular anisotropy of Co-Cr films.
A new sputtering target was proposed for high-rate deposition fabrication of double layer perpendicular media. The target consisted of Permalloy plate walls which were perpendicular to the substrate and worked themselves as a part of the magnetic circuit for plasma confining. Discharge characteristics of the target were very preferable for low-pressure and high-power sputtering at a low discharge voltage. Obtained Permalloy films showed a wider homogeneous thickness region and much stronger adhesion to a polyimide substrate compared with a conventional GT target.
CoCr/NiFe double-layered perpendicular media were sputter-deposited on Nip-plated aluminum substrates. The crystal orientation and magnetic properties of the CoCr layer on the NiFe layer are poorer than those of the CoCr layer on Nip. In order to improve the properties of the CoCr layer on the NiFe layer, the effects of the NiFe underlayer were investigated with respect to the surface roughness, crystal orientation, and crystallinity. It was found that the crystallinity of the NiFe layer strongly affects the crystal orientation of the CoCr layer. Both bias sputtering and low residual gas pressure were effective in improving the NiFe crystallinity. The c-axis dispersion angle (Δθ50) as small as 1.6°was obtained for the CoCr layer on the NiFe layer with high crystallinity.
It is well known that recording and reproducing characteristics at short wave length are influenced by surface roughness of the magnetic recording media. The surface roughness is usually measured by a surface roughness measuring apparatus using an index such as RMS, Ra, or Rmax. Since these indexes are defined for general use, it does not always follow that these indexes are suitable to evaluate the surface roughness. Therefore, a new index was studied using computer simulations, which are concerned with the distance between media surface and a head gap. On the simulations, the head is scanned on the surface of the recording media and the distance is calculated by spacing loss factor. The new index is useful in evaluating the surface roughness of contact recording media, especially to compare that of different kinds of recording media.
Magnetization and Mössbauer spectra were measured for three kinds of Fe4N powders made from acicular α-FeOOH, α-Fe2O3 and carbonyl iron powders. Except for the Fe4N powder from carbonyl iron, the saturation magnetization was lower than the bulk value (190 emu/g). A large amount of oxygen and a small amount of Ni, Zn and Si were detected in the sample from α-FeOOH. According to the Mössbauer spectra, it was concluded that the decreases in the saturation magnetization were mainly due to the coexistence of a paramagnetic phase. A large quadrupole splitting of the paramagnetic peak indicates that the paramagnetic phase may be an oxide consisting of Fe(II) ion, e. g., wustite. In addition, it is considered that Ni and Zn preferentially substitute Fe at the corner of fcc-Fe4N and also reduce the magnetization.
Co-Ti substituted barium-ferrite fine particles (500 ∼1000Å) with high dispersibility and high uniformity in size were fabricated by hydrothennal synthetic method accompanied by heat treatment, and their magnetic properties were studied. X-Ray diffraction, Mössbauer, magnetization measurements and electron microscopy were used for the characterization. Superior magnetic characteristics, which can cornpete with by other reported methods, were obtained by the present method. Mössbauer spectra with 16.4 kOe applied parallel to the γ-ray show the formation of magnetic easy cone for Co-Ti substituted bariumferrite, that can be the origin of an abrupt magneticsoftening of this system with a small amount of substitution. Increased saturation magnetization was obtained by lowering the Ti contents from equimolecular ratio with Co ions.
A Sendust MIG head was constructed with oxide or noble metal layer being deposited at the interface between Sendust film and ferrite. An A.E.S. study indicated that the deposition of barrier films such as Ir, Pt or SiO2 prevented the thermal diffusion of oxygen and hence the oxidation of Sendust film at the interface. Intensity of X.R.D. peak from (110) Sendust initial layers deposited on the barrier film/ MnZn-ferrite were larger than that from the one directly deposited on MnZn-ferrite. Thus the MIG head constructed with Ir or SiO2 film being placed between Sendust film and MnZn-ferrite showed successfully reduced secondary gap effect.
Recording characteristics and wide band reproducing characteristics were investigated for laminated heads composed of Co-based super-structured nitride alloy films. The super-structured alloy film is composed of 250Å thick non-nitride and nitride layers of Co-NbZr and has higher thermal stability, higher saturation flux density, and higher initial permeability at high frequency region than conventional Co- Nb-Ta-Zr amorphous alloy film. Because of these excellent properties, high recording performance and wide band reproducing characteristics were achieved by laminated heads with narrow gap length.
Eighteen tracks two layers thin film write head using all dry process has been developed for the magnetic tape drive system. Production process has all dry process performed by sputtering and ion milling process repeatedly. At the smoothing process two kinds of resists were used and 200Å maximum step was observed. Front taper angle controlled between 30 degrees to 45 degrees. We developed the material for full write by using Co-Nb-Zr-Ta amorphous alloy having high Bs(Bs=12000 Gauss). Co-Nb-Zr-Ta amorphous film has been sputtered by Bias Sputtering. AYA-2L (Active Yoke by Amorphous-2 Layer) head has been developed as enhanced all dry write head.
Permeabilities of soft magnetic films (sputterd CoNbTaZr) were measured under the wide range of field amplitude (8 mOe∼8.5 Oe) with high frequencies (10k∼1 MHz). In order to display the frequency (f) dependence of permeability simultaneously with its field-intensity (Hex) dependence, an expression method for permeability characteristics was proposed employing the display of contour-lines of permeability values on the Hex-f plane. It was found that the contour-line patterns reflect the technical magnetization process of the soft magnetic films at each area on Hex-f plane. Especially in the case of film having uniaxial magnetic anisotropy, behaviors and implications of the contour-line patterns were investigated. The permeabilities and the magnetization processes are different from those under different magnetic exciting ways, even at the same values of Hex and frequency. This difference may be attributed to the irreversible movement of magnetic domain-walls.
Reproduced waveform with thin film magnetic heads, distortions (wiggles) of reproduced waveform are sometimes observed. In this study, a method for extracting wiggles from reproduced waveform was devised, and wiggle behavior was studied. Extracted wiggles were in pulse width from 40 to 80 ns, in amplitude from 10 to 30μV, and their locations during reproduced waveform were shifted by and external magnetic field, but wiggle width and amplitude were not affected. After write operation, wiggle pulse width and amplitude changed; however, the area under the extracted pulse was verified constant. Peakshifts of reproduced waveform increased when wiggles came close to the peak of the reproduced waveform, and wiggle amplitude increased.
As magnetic disk surface becomes flatter and smoother, the problems of head crash and stick slip will become more serious. Therefore, various quantities on head movement in CSS have been measured comprehensively. As a result, it has been made clear that it is necessary to prevent the head from breaking the liquid lubricant by falling forward onto disk surface and to make it float on the liquid lubricant by lifting backward when frictional force acts on it. Therefore, "a self-peeling suspension" which does its operation statically and "a head with center gravity back" which does it dynamically have been developed. Both of them have realized a good sliding situation on flat and smooth disk.
The preparation method and softmagnetic properties of electrodeposited Fe-Co-Ni-Cr alloy film having high saturation magnetization and single phase structure were investigated. It was found that Fe-Co-Ni-Cr alloy film having a single phase fcc structure can be electrodeposited at the cathode in a solution composed of Fe2+, Co2+, Ni2+, Cr3+ ions and SO42- ions as count anion by plating under a condition of the current density more than 30 mA/cm2. The film composed of Fe44Co17Ni36Cr3 alloy prepared by the plating method described in this paper has the soft-magnetic properties (μiHA>1500, HcHA< 0.5 Oe, λs=6 × 10-6Bs= 16800 Gauss) applicable for HDD thin film magnetic head cores.
Zig-zag transitions were surveyed from the viewpoint of writing head field. The transition region of magnetization reversals on sputtered thin-film-media written by ferrite and MIG head was observed by the colloid-SEM method, since the transition region remains clear without any Bitter ferrofluid decoration. The head field was analyzed by using a finiteelement method with magnetic saturation taken into account. The MIG head exhibited a shorter transition length i.e. having advantage for high-density recording, than the ferrite head. The sharp writing field from the MIG head, which is based on unsaturation of metal-film within the gap region, yields a short transition length. The transition length of both MIG and ferrite head strongly depends on the field gradient as proportional to (∂Hx/∂X|Hx=Hc)-0.5.
Side-fringing fields of thin film heads were studied with three dimensional simulation. Readback signals were calculated by the principle of reciprocity. Outputs as a function of linear density were calculated by superposition of isolated pulses. The three dimensional calculation of isolated pulses, off-tracks and outputs as a function of linear density, correspond to these measurements. From the calculations and measurements, the effect of side-fringing field appears in isolated pulses of narrow track heads. It was found that asymmetry of isolated pulses results from the effect of side-fringing field. By narrowing the track width, the effect of side-fringing fields increases. Readback pulses from the outside of the track are broader than ones on the track center and therefore resolutions of narrow track heads decrease.
A 3-dimensional medium magnetization model was developed to analyze recording performances for particulate coating media. Using an FEM program incorporating this model, we investigated the recording process by a ring head with respect to effects of changes in distributions of easy-axis direction and anisotropy field strength, that is, distributions of orientation, size and shape of particles. It was shown that the sharper anisotropy field distribution gives larger remanent magnetization in the medium at high recording densities but sharper easy-axis distribution does not improve the high density recording characteristics, because an AC erasure-like effect becomes dominant owing to the broad perpendicular field component of a ring head.
The fundamental study was performed to investigate the feasibility of multi-track recording. It was confirmed that the side-writing or -erasing effects of a single-pole type perpendicular magnetic head are negligibly small. It was also found that the perpendicular head posesses uniform reproducing sensitivity in trackwidth direction of a main-pole. These results show that perpendicular recording is suitable for multi-track recording and full-track reproducing using multilevel recording.
A disk-drive head combining a shunt biased MR read element and a multi-turn inductive write element is designed for a 2.5″ hard disk drive and was used for these expriments. The MR element, which consists of Ni-Fe film, exists in the inductive write gap. The write core consists of Mn-Zn ferrite and Co-Zr-Nb-Ta amorphous film. It has a Shaped Rail Air Bearing Surface to obtain high reliability at low flying height, such as 0.15μm. Output of 0.54 mVp-p in longitudinal recording and 0.35 mVp-p in perpendicular recording were obtained for the MR-inductive combination head at 4.7 m/s media velocity, 0.15μm flying height and 10.0μm track width. Moreover, in spite of the fact that the MR element did not have center tap, it could decrease second harmonic distortion under -26 dB.
The capability of contact perpendicular magnetic rigid disk recording was investigated by non-flying single-pole heads. Double-layered magnetic films for perpendicular magnetic recording were made by RF sputtering on non-texturing glass substrates. A novel head supporting and sliding method was introduced to make a contact rigid disk recording. The head can be floated by this at an extremely narrow spacing of 20 to 30 nm on the disk under its self-weight less than 1 g. Using the non-flying head slider, not only similar high density recording characteristics were obtained but also remarkably high durabilities of the heads and the disks were observed as comparable to those in contact recording and reproducing on flexible perpendicular magnetic disks.
MnAl films prepared in a form of multilayer Mn/Al by vacuum evaporation were investigated. In the Mn content-range of 31∼40 at.%, the films become ferromagnetic (τ-phase) by annealing between 220∼ 420°C. They show the same X-ray diffraction lines of fct(Cu-Au I) structure as bulk MnAl alloy, although the Mn composition range for the τ phase is quite different from that of the bulk; 51-59 at.%. In the films, τ-phase is mixed with a nonmagnetic η-phase below 34 at.% Mn and with a β-phase above 36 at.% Mn. Ms changes with Mn content and shows a maximum of ∼330 emu/cm3 at about 36 at.%Mn. Hc increases from 1 to 6 kOe with increasing Mn content. The θk increases with decreasing wavelength λ and obtains a value of about 0.17° at 400 nm. while the reflectivity R has a value of above 40% in the visible wavelength range.
Mn2Sb films prepared by vacuum evaporation are known to form perpendicularly magnetized films. The doping effect of Bi and Cr in Mn2Sb films on magnetic and magneto-optical properties was investigated over a large amount of doses up to 26 at.% for Bi and 16.4 at.% for Cr. Perpendicular magnetization characteristic maintains even at such heavy doped films but the substitution of Bi for Sb is estimated to be about 8 at.% in Mn2Sb and the excess Bi is precipitated at the free surface of the films from magnetic and AES measurements. Magneto-optical Faraday rotation angle at λ=633 nm is decreased by increasing the amount of the dose. As Bi and Cr modified Mn2Sb intermetallic compounds are known to have the first order phase transition from anti-ferromagnetism to ferrimagnetism, these films (especially Cr doped films) may be applicable to temperature sensor by making use of the phase transition temperature.
NiAs-type Mn(SbBi) alloy films, whose c-axes were oriented perpendicular to the film surface, were obtained in the composition range, 45 < Mn < 65 at.%, Bi < 10 at.% by the following method. The first step was the formation of oriented SbBi layer annealing, the second step was the deposition of the Mn layer onto this SbBi layer at appropriate substrate temperature and the last step was the annealing of this film up to 500°C The several phases appeared in these films. Matrix of the films was NiAs-type Mn(SbBi) phase. It was found that the phases and lattice constant for Mn(SbBi) changes by increasing the annealing temperature. Systematic experimental of magnetic anisotropy constant, Ku, and Kerr rotation angle, θk, was carried out for Mn(SbBi) films. As a result, a substitution of Bi for Sb led to 1) increasing Ku value and 2) change of the wave length dependence of θk. It was observed that the maximum values of Ku and θk were 4.5 × 106 erg/cm3 and 0.5° at Hex = 7 kOe.
The magneto-optical Kerr rotation angle θk. for a polished surface of bulk PtMnSb was measured at 632.8 nm in high magnetic fields. The saturation value of θk for the stoichiometric sample was 1.42° in the as-polished state, and it was enhanced to 1.75° by annealing at temperatures higher than 400°C It is suggested that the enhancement of θk is caused by the decrease in the imaginary part of the diagonal element of dielectric constant. It was also found that θk depends strongly on the composition in the Pt-Mn-Sb ternary system and takes a maximum at the stoichiometric composition.
Dependence of magnetic properties and Kerr effects in PtMnSb thin films on oxygen partial pressure during annealing was investigated. Coercivity Hc(⊥) increased as the oxygen partial pressure increased, while the change in Hc(//) was relatively small. Saturation magnetization (Ms) was almost constant up to 6 × 10-4 Torr, and then decreased rapidly above that pressure. Kerr rotation angle at nonmagnetic field (θk(0)) and square ratio (Rs) of Kerr loops have maximum values at around 8 × 10-4 Torr and these are 0.85° and 0.45, respectively. SEM observation and X-ray diffraction clarified that these values are related to the preferential oxidation at PtMnSb columnar boundaries. The oxidation may shorten the size of columns and isolate them from each other.
We investigated the crystallographic and magneto- optical properties of Cd1-xMnxTe films grown on (100) GaAs substrates. The growth of either (111) or (100) oriented Cd1-xMnxTe film on a (100) GaAs substrate was successfully controlled by changing the electron current Ie for ionization or the acceleration voltage Va. This different film growth was considered a result of a change in nucleus formation in the initial stage of film growth by the electric charge and kinetic energy of ionized clusters. From measuremerits of the Kerr rotation spectra, it was found that the Faraday rotation of the films on a GaAs substrate exhibited the same characteristics as those on a sapphire substrate.
Direct overwrite method by light intensity modulation using only an external magnet is described. The film consists of exchange-coupled RE-TM alloy quadrilayer. Good recording characteristics were obtained, such as C/N ratio>47 dB on a bit length= 0.76μm without a residual signal. The initializing process of the 2nd layer is one of the most important ones. It was found through M-H loops that the 2nd layer has two different coercivities for the magnetization states of other layers and coercivity of the 2nd layer is smaller than that of the single layer in the case where the sub-lattice magnetization of the 1st layer is anti-parallel to the 4th layer. Therefore, these phenomena assist the 2nd layer to be initialized.
Characteristics of magnetic field modulation recording on GdDyFeCo magneto-optical disk were investigated. GdDyFeCo recording layer was deposited by two source RF magnetron sputtering method. The compositionally modulated films changed their thermo-magnetic properties with the modulation periodicity and exhibited minimum recording field (Hs) value at modulation period of 2Å. According to the observed dependence of Hs on GdDy contents, relatively low Hs value was obtained in the rare-earth rich region near the compensation composition. By optimizing the GdDy contents, recording magnetic field transition time less than 250 ns could be obtained at recording frequency of 720 kHz.
It is possible to estimate an ellipticity of reflected light from a magneto-optical disk by finding the value of the pick up phase difference whick gives maximal amplitude of the read out signal. Optical pick up with phase compensator and half wave plate which has variable phase difference and rotatable polarized plane of incident light to disk was prepared. Two contributions to ellipticity, substrate retardation and Kerr ellipticity, were separated by measurement of ellipticity in case the polarized plane of incident light is parallel and perpendicular to the groove. The result indicate that polycarbonate disk had a greater contribution of substrate than glass disk did. Also it was clarified that the temperature dependence of ellipticity came from variation of substrate retardation.
The author has developed a new method to measure the effective magnetic anisotropy field H′k of RETM magnetooptical recording film using the spontaneous Hall effect. By this method, H′k can be obtained from the measurement of the spontaneous Hall loop with respect to the magnetic field applied in an oblique direction of 45°from the film normal. The value of H′k obtained from the Hall method agrees fairly well with those determined by the classical VSM/torque method. This paper introduces the new method and presents the experimental results.
Amorphous ribbons of Nd11Fe72Co8B7.5V1.5 alloy were prepared at a substrate surface velocity of 20.7 m/s by the single roller rapid-quenching method, and the effect of annealing treatment on the magnetic properties was studied. The optimum annealing condition was at 650°C for 5 min. and then the value of (BH)max of crystallized ribbon was 148.6 kJ/m3. From TEM observation, the fine grains of the ribbons crystallized from the amorphous state was from 25 to 33 nm in diameter. The temperature coefficients (from 25 to 125°C of Br and HcJ for ribbon crystallized of Nd11Fe72Co8B7.5V1.5 alloy were -0.083%/°C (reversible) and -0.375%/°C (irreversible), respectively. The maximum energy product obtained in Nd11Fe72Co8B7.5V1.5 bonded magnet prepared by using the ribbons annealed at 650°C was 94.2 kJ/m3, and then this bonded magnet density is 6.25 Mg/m3.
Melt-spun ribbons and sintered materials with the composition of Nd15(Fe1-x-yCoxNiy)77B8 were investigated with respect to saturation magnetization, coercivity, Curie temperature and corrosion characteristics. It was found that double substitutions of Co and Ni atoms for Fe atoms enhance the intrinsic coercivity of sintered magnets for compositions of 0.2≤x≤0.4 and 0.0≤y≤0.2, and improve corrosion resistance. A further addition of Ti atoms to the system increases the coercivity and makes the demagnetization curve rectangular. For example, (BH)max and intrinsic coercivity in Nd15(Fe0.585Co0.30- Ni0.10Ti0.015)77B8 amount to 33.8 MGOe and 10.4 kOe, respectively.
Magnetic field induced-magnetic anisotropy and thickness dependence of magnetic properties were investigated in nanocrystalline alloy “Finemet”. It was difficult to induce the magnetic anisotropy in Finemet at a low-temperature range as compared with amorphous alloys. However, the magnetic anisotropy in Finemet could be easily induced by annealing over 700 K, and increased with increasing the annealing temperature and time. Magnetic properties of Finemet in a high-frequency range were improved with decreasing thickness. This thickness dependence was similar to that for Co-based amorphous alloys. Thin Finemet materials are especially available for the magnetic components applied in a high-frequency range, because of their low core losses and high permeabilities in a high-frequency range.
Fe-rich and Co-rich amorphous magnetostrictive wires have shown sensitive bistable flux reversal (large Barkhausen effect or re-entrant flux reversal) characteristics. Fe-Co, Fe-Cr and Fe-Ni system amorphous wires were made and their various magnetic properties (Ms, Mr/Ms, Ku, λs, H*, and λsMs/Ku) were measured for investigation of general properties concerning the large Barkhausen effect and stress sensitivity of the amorphous wire. Domain* wall propagates through an inner core with the diameter of about 1/√2 that of the positive magetostrictive wires, while about l/√3 that of negative magnetostrictive wires. Stress sensitivity of magnetization was analyzed using a figure of merit F expressed as (3/2)λsMs(1-(Mr/Ms)2)(Mr/Ms)/Ku.
Technology for the world's first production of 6.5% Si steel sheets has been commercially developed in coil-form. The DC and AC magnetostriction in 6.5% Si steel sheets and the noise of the transformer made of 6.5% Si steel sheets were investigated in comparison with that of conventional 3% Si steel sheets. 6.5% Si steel sheets showed extremely low magnetostriction and were recognized to be suitable for application to the low noise audio frequency transformer.
New single crystal 6.3%SiFe wires with a diameter of less than 90μm and the length of 7∼30 cm were developed by TOYOBO Ltd., R & D. Sensitive and complete bistable flux reversal (large Barkhausen effect or re-entrant flux reversal) was found in these wires similar to that in amorphous magnetostrictive wires. The single crystal 6.3%SiFe wire shows almost zero-magnetostriction. The mechanism of domain-wall propagation along with the wire axis is analyzed. Pulse generation characteristics are measured for various magnetic fields and stresses.
Scattered magnetoelastic waves were observed in as-quenched and annealed amorphous Fe-Si-B wires in order to clarify the nature of the scattering centers. Neither magnetic field nor tensile stress applied to the wire change the waveform of the scattered wave. Scattered waves observed in annealed wire show that the annealing process has no significant effect on the properties of the scattering centers. These experimental results indicate that the scattering centers are caused by fluctuations of some elastic properties along the wire introduced by the quenching process, and that they have an average interval of a few millimeters.
Amorphous Co-ferrite thin films not containing glass formers were prepared by ion beam sputter deposition. Their magnetic properties were invetigated by means of low field dc magnetization and ac susceptibility measurements, which gave evidence of spin glass behavior. Temperature dependence of magnetization in an external field of 50 Oe exhibited an irreversibility below nearly room temperature, which decreased with increasing field. A cusp corresponding to spin freezing temperature was observed at 284 K in ac susceptibility measured at 80 Hz, 1 Oe. Below this temperature, relaxation of thermoremanent magnetization was observed. Besides this transition at 284 K, a sharp peak which suggests another transition was observed at 86 K in ac susceptibility. It is considered that the spin glass ordering with a high spin freezing temperature is mainly caused by amorphousization for strong super-exchange interactions.
For Fe film made by obliquely simultaneous evaporation from two sources with an angle ψ between two incidence planes, magnetic anisotropy in film plane was measured and columnar structure was observed by SEM. For ψ ≤ 45°, easy axis of anisotropy and alignment of columnar grain lie in the direction perpendicular to the bisectional plane of the two incidence planes. For ψ ≥ 45°, they lie parallel to the bisectional plane. A mechanism of anisotropic arrangement of columnar grain was proposed from the view point of self shadowing. The magnetic anisotropy calculated from the columnar structure based on such mechanism, agreed fairly well with the measured one.
The shape of magnetoresistance curve is discussed based on the rotation model of magnetization. The magnetoresistance curve exhibits a dip when the magnetic field deviates from the hard direction of magnetization. The deviation of the direction of electric current causes an irreversibility in magnetoresistance curves. These results indicate that the dip and/or irreversibility being independent of the Bulkhausen effect should be taken into account for the explanation of those observed experimentally. An asymmetric magnetoresistance curve observed sometimes in 82Ni-Fe permalloy films is explained by the model with the assumption of magnetic inhomogenity. Also, the shape of magnetoresistance curves observed in Co/Au multilayer films with perpendicular magnetic anisotropy is explained by the model.
The relation between the anisotropic magnetoresistivity ratio Δρ/ρ0 and ordinary Hall coefficient R0 and extraordinary Hall coefficient Rs were studied for Ni-Fe binary alloy and (Ni89.5Fe10.5)M (M =Co, Cu, Nb, Gd, Al, Si and Bi) ternary alloy thin films, to obtain a guiding principle of searching the new materials that show a large value of Δρ/ρ0. The value of Δρ/ρ0 increases with increases in the absolute value of R0 and also shows a maximum (Δρ/ρ0≅4%) at Rs= 0. In the case of the ferromagnetic metals, the large value of Δρ/ρ0 is obtainable under the following conditions, (1) sign of R0 is negative and the absolute value of R0 is large (carrier is electron like and effective carrier density neff is small) and (2) Rs is zero
The magnetic domain structures of thin film head with NiFe films, driven by DC and AC currents, were investigated in order to evaluate the magnetization process under high frequency magnetic field using spin-polarized SEM. The image contrast under high frequency magnetic field was calculated as the time average component of the magnetization along the detection direction for the magnetization rotation and the reversible domain wall movement. From the relation between the observed domain images and the calculated distribution of the average magnetization about the domain wall, it was found that irreversible domain wall movement occurs in the overall magnitc core under the high frequency excitations. A domain wall moves slightly and reversibly until the direction of the magnetic field attains reverse under the high frequency excitation.
A magnetic force microscope (MFM) has a potential for observation of fine magnetic domain structure, but has some problems to be overcome. As a result of theoretical analysis, the most suitable value of parameters was determined as tip-sample distance h=600Å and tip radius R= 100Å. Using these parameters, the MFM cantilever having a length of 130 μm, a width of 10μm and a thickness of 1μm was designed. A scanning tunneling microscope (STM) was used for detection of the cantilever deflection resulted from the magnetic force. Bringing sharp Fe wire tip close to a sample to observe the influence of tip stray field, a new domain configuration was observed by scanning electron microscopy (SEM).
Polycrystalline Fe3O4 films were plated on glass substrates in an aqueous solution. By irradiating the substrate surface with an Xe-lamp at ∼450 W/cm2 power, the deposition rate of Fe3O4 film was increased by a factor of ∼10 (from ∼30 nm/min to ∼320 nm/min). With light exposures as short as 4 min we obtained ferrite films of ∼2μm thickness. We believe that the effect of the light is to raise the temperature. X-Ray analysis revealed that the films were polycrystalline spine1 with no preferred crystal orientation, scattering due to impurity phase being not observed.
Nonthermoequilibrium garnet Bi3Fe5O12 is obtainable by direct epitaxial growth onto a single crystalline garnet substrate via vapor phase. Using a reactive ion beam sputtering technique and a target composed of 3Bi2O3 and 5Fe2O3 in molar ratio, variation of crystalline phase with substrate material was widely investigated. The substrate materials examined were fused quartz, sintered alumina, and single crystals of MgO, SrTiO3, MgAl2O4 and Gd3 (ScGa)5O12. The substrate temperatures examined were room temperature, 480 and 540°C. The garnet phase did not occur on the substrates except for the single crystalline garnet. Thermoequilibrium phases, BiFeO3 and Bi2Fe4O9, were only formed on the alumina substrate. A new nonthermoequilibrium oxide composed of Bi : Fe=3 : 5 in molar ratio was formed on the fused quartz, MgO, SrTiO3 and MgAl2O4 substrates by crystallizing during deposition. The oxide was revealed to be antiferromagnetic at'room temperature.
Bi, Al substituted YIG was synthesized by sol-gel method using a solution of yittrium, iron, bismuth and aluminum nitrates dissolved in ethylene glycol. Films were fabricated by spin-coating a gel solution onto glass substrates. Film thickness was controlled by repetitive spin-coating several times. Coated films were subjected to heat treatment in air at 700°C for 4 hours to obtain YIG crystal. Magnetization of the films with BixY3-xFe5O12 lies in the film plane. The films magnetized normal to the film plane were obtained at a composition of Y1.5Bi1.5Fe3.8Al1.2O12,but magnetization tends to incline toward the film plane with increasing film thickness. This may be explained in terms of stress due to substrate constraint: Stress relief becomes remarkable as thickness increases by repetitive spin-coating. This can be, to a great extent, eliminated by heat treatment after each spin coating process. Magneto-optical Faraday rotation of the films are shown in comparison with both heat treatments.