The ThMn₁₂-type hard magnetic compounds composed of rare earth elements (R) and 3d ferromagnetic transition metals such as Fe and their interstitially- modified compounds have been known for many years as possible candidates for development of permanent magnet materials. Being the family of compounds of the lowest rare earth contents among known R-Fe compounds, this class of materials attracts renewed interests especially after the discovery of NdFe₁₂N that showed intrinsic magnetic parameters that surpassed those of Nd₂Fe₁₄B (Y. Hirayama, Y.K. Takahashi, S. Hirosawa and K. Hono, Scripta Materialia 95 (2015) 70). In this paper, recent topics related to this class of materials are overviewed and future perspectives are discussed.

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The La-Co substituted magnetoplumbite type (M-type) hexagonal ferrites are known to have the higher magnetic crystalline anisotropy compared with conventional M-type Sr ferrites. The site occupation of cation in the crystal structure has been analyzed by neutron diffraction and EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy in order to clarify the correlation between the local structural change and the improvement of the magnetic anisotropy. The EXAFS analysis has suggested that Co ions were located in the 4f₁, which showed good agreement with the results by neutron diffraction and XMCD analysis.

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This paper reviews recent progresses in coercivity improvement of hot-deformed anisotropic Nd-Fe-B magnets by the low temperature grain boundary diffusion process using RE₇₀Cu₃₀ (RE = Pr, Nd) eutectic alloys. Using Pr₇₀Cu₃₀ alloy, the coercivity was enhanced from 1.60 T to 2.56 T. The hot-deformed samples are expanded along only c-axis direction after the diffusion process by the formation of thick Nd-rich grain boundary phase parallel to the c-planes of platelet shaped Nd₂Fe₁₄B grains. To suppress the reduction in remanence caused by the excess expansion during the diffusion process, we developed an expansion constraint eutectic diffusion process. We demonstrated high performance Dy-free anisotropy magnet with coercivity, µ₀H_c = 1.94 T, and remanence, B_r = 1.35 T, by the expansion constraint diffusion process using a Nd-Cu alloy as a diffusion source.

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The hot-deformed Nd-Fe-B magnets are known to have a fine microstructure due to their unique fabrication procedure. It is well known that coercivity increases with decreasing grain size of a hard magnetic material. Therefore, a hot-deformed magnet can possess good magnetic properties without being composed of heavy rare-earth elements such as Dy and Tb. In this paper, we present the characteristics of hot-deformed magnets of a newly developed material in detail.

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The rare earths group consists of 15 elements from Lanthanum to Yttrium and these 15 elements are contained in the rare earths ores. The composition of each ore depends on the mine where the ore is mined. The fractions of 15 rare earth elements are, however, different from the global applications. Currently most of rare earth separating plants face a financial problem. The standard Cerium Oxide is now sold at around $3/kg, which cannot cover even only the operating cost in the rare earths separation plant. This problem is caused by the extreme unbalanced situation of supply and demand. There are large excesses of supply in Cerium, Yttrium and Samrium. This is not only the problem for the rare earth suppliers but also for users. All participants in the rare earth supply chain must take account of this problem and take actions to solve it.

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The magnetic properties of Nd-Fe-B magnets with 0.5mm and 1mm cubes in size were measured with a vibrating sample magnetometer equipped with High Temperature Superconducting Magnet (VSM_HSC). With the VSM_HSC, high sweep speed and high accuracy in magnetization measurement were achieved. Furthermore, magnetic properties of Nd-Fe-B magnets were measured with the VSM_HSC, Pulsed Field Magnetometer and a Permeameter. It was found that the squareness of demagnetization curves appeared depending on the measurement systems.

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Improvement in the magnetic properties of PLD (Pulsed Laser Deposition)-fabricated isotropic Fe-Pt film magnets by controlling laser energy density, which strongly affects the numbers and/or size of droplets, was carried out. The use of laser energy density range from 10 to 25 J/cm² enabled us to obtain Fe-Pt films with relatively a little amount of droplets. Resultantly, we could enhance the value of (BH)_max up to approximately 125 kJ/m³ which is comparable compared with that of a sputtering-made Fe-Pt film magnet.

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It was reported that excessively added Ca at the timing of raw materials mixing and added CaO before sintering have a close relationship on the magnetic and physical properties of Ca-La-Co ferrite sintered magnets. In this study, the effects of the total amount and the ratio of excessively added Ca at the timing of raw materials mixing and before sintering on the magnetic and physical properties are discussed. The results show that the coercive force at low sintering temperature and the magnetization of sintered samples at the same density decrease with an increase the Ca excess total amount. Moreover, the magnetization at the same density decrease, and the density of sintered samples at same sintering temperature gradually increase with an increase excessively added Ca at the timing of raw materials mixing.

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Nd₁₅Fe₇₇B₈,Nd₄Fe_77.5B_18.5,and R-Cu (R=Nd, Pr, Sm, Ce) eutectic alloys were produced by the melt-spinning technique. The Nd-Fe-B alloys mixed with the Nd-Cu alloy were annealed to examine the effects of the Nd-Cu alloy on the coercivity of the Nd-Fe-B alloys. The coercivity of the Nd-Fe-B alloy increased as the amount of the Nd-Cu alloy increased. The Nd₁₅Fe₇₇B₈ alloy mixed with 30% Nd-Cu alloy exhibited an unusually high coercivity of 29.2 kOe after annealing at 873 K for 1 h. It was found that the coercivity of the Nd₄Fe_77.5B_18.5 alloy was also increased by the addition of Nd-Cu alloys. The Nd₄Fe_77.5B_18.5 alloy mixed with 40% Nd-Cu alloy showed a coercivity of 4.6 kOe after annealing at 923 K for 1 h.

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In this study, we investigated the effect of intermediate-heat-treatment on the microstructure and magnetic properties of Sm(Co_bal.Fe_0.35Cu_0.06Zr_0.018)_7.8. It was observed that grain size is increased by the intermediate-heat-treatment. In such specimens, we found that squareness was clearly improved and (BH)_max of 271 kJ/m³ was obtained. These results indicate that reducing the fraction of grain boundaries by increasing the grain size affects the behavior of domain-wall motion.

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Junior high school and high-school students learn the concept of velocity and acceleration using experiments with dynamic carts and recording timers. Problems with recording timers are, however, that it takes a long time to read the dots and do not promote intuitive understanding. In recent years smart devices are applied to physics education because of internal many motion sensors. We propose accelerated motion experiments support software (AES) for smart devices that improve the above problems. Experiment system with AES is used in accelerated motion experiments for students at ibaraki national college of technology, cutting down classroom time and educational effectiveness are discussed in this paper.

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In hyperthermia treatment, the accurate temperature measurement of tumor region is vital to determine the therapeutic effectiveness of heating. Conventional methods require thermal probes to be inserted invasively into tumor region. However, by using Ferromagnetic Implant with Low Curie Temperature (FILCT) as thermal probe, we have developed a wireless temperature measurement method that can noninvasively measure the temperature of tumor region from outside of the body. To make the approach feasible in clinical settings, challenges remain when dealing with body motion artifact. When the material is injected into tumor region, the relative position between the magnetic field supply and detection (MFSD) unit and the material is supposed to fluctuate with periodic respiration and heartbeat. In physical experiments, the FILCT temperature cannot be detected, because the detection voltage was buried by the artifact noise (SN ratio=-3.1 dB). Hence, this study proposed a body motion artifact reduction method by rotating scanning the MFSD unit in a different period cycle from body motion. By extracting the power spectrum synchronized with the rotary scanning, we confirmed that regardless of presence of body motion, the change of the power around Curie point is sufficiently large to detect whether treatment temperature has been reached.

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We have developed a novel reconstruction method for a laser interferometer to determine the radial electron density profile in a cylindrical plasma vessel under an axial symmetrical assumption with spline interpolation. This method can extend the reconstructible area out of the line-integrated density measurement area by using the additional local measurement data. Although both the ordinary Abel inversion and the basis function expansion method cannot reconstruct well out of the measurement area, the new method can reconstruct distributions even with non-zero electron density on the wall. In order to confirm the validity of the method, the error sensitivity is evaluated by Monte Carlo simulation.

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A new biodegradable dielectric fluid for transformers, palm fatty acid ester (PFAE), with better cooling performance and oxidative stability than conventional mineral oil (MO) was developed in 2008. In this report, the thermal aging characteristics of Kraft paper (KP) in PFAE and MO were compared in air sealed tanks, in order to evaluate the applicability of PFAE to pole transformers. The degradation of paper impregnated in PFAE and MO was compared with degree of polymerization (DP) and tensile strength (TS). The electrical properties of PFAE and MO after aging were determined. The DP of the KP aged in MO is nearly half of that in PFAE after 365-day aging at 105°C. The TS of the KP in PFAE after 365-day aging at 105°C decreases to about 78% of initial strength, while the TS for the paper in MO drops to 15%. After 365-day aging at 105°C, the breakdown voltage of aged PFAE is 76kV, while that for aged MO is 20kV; the dissipation factor of aged MO increased over 100 times, while that for PFAE kept the similar value. The production of sludge in aged MO makes it black, while aged PFAE keeps its transparence. Additionally, the mechanism on the suppression of KP degradation in PFAE is proposed.

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Using a velocimeter based on the laser Doppler effect, we measured spark lengths by moving a grounded metal-plate to an electrostatic discharge generator with charge voltages from 1000 V to 8000 V at three different approach speeds of 20 mm/s, 100 mm/s and 200 mm/s. As a result, we found that with increasing the approach speed, spark lengths decrease, while the resultant breakdown potential gradient or the charge voltage divided by the spark length exponentially increases.

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We fabricated a visual observation system for a rotating object with an automatic synchronizing function using a ferroelectric liquid crystal (FLC) cell. Stroboscopic vision was achieved not using a flash light but using a FLC cell as a fast-response optical shutter. A reflective photosensor was used for sensing a rotating object. For the drive of the liquid crystal shutter synchronized with the rotating object, an electric circuit mainly composed of a microcontroller and a H bridge unit, which were made up of easily available electric parts, was designed. The automatic synchronizing function was evaluated from the visibility of a character on the center of the propeller. The results indicate the automatic synchronizing function can work over 6.2 × 10³rpm.

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High performance visible-light-responsive photocatalysts were prepared by naturally oxidizing a TiO₂-coated Cu plate or a sintered TiO₂-coated Cu plate at 573 k for 1 h. The performance of the prepared photocatalysts were 5 to 6 times higher than a nitrogen doped TiO₂ photocatalyst, which is one of the most famous visible-light-responsive photocatalysts.

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