Akira Fukuno

Large particle size Sm2Fe17Nx compounds by hydrogen treatment

Large particle size Sm2Fe17Nx with a low oxygen content has been produced by treating Sm2Fe17 with hydrogen before nitrogenation. Large Sm2Fe17Nx particles of more than 2 mm include nearly 3.0‐wt. % nitrogen and a magnetization level of 140 emu/g. The hydrogen decrepitation behavior was not observed for this alloy and the size of samples were not changed after hydrogen treatment and nitrogenation. It is thought that hydrogen absorption and desorption increase the gas‐solid reaction area significantly. The oxygen content of these particles is less than 200 ppm because the fine pulverization step was skipped. The relation between the nitrogen content and magnetization of Sm2Fe17Nx will be presented.

A comparison of magnetic anisotropy constants and anisotropy fields of permanent magnets determined by various measuring methods

Uni-axial anisotropy constants and uni-axial anisotropy fields of oriented polycrystalline magnets were obtained from the field-dependence of the magnetization by three methods and from torque measurements. The results from torque measurements are found to be superior to those from the intersections of magnetization curves for fields parallel and perpendicular to the preferred axis, the integral of the perpendicular magnetization and the maximum in the second derivative of the perpendicular magnetization, called the singular point detection (SPD) method. Sintered Sr ferrite magnets can be considered as quasi-single crystals because of their high degree of orientation and their large crystal grain sizes in the range . A value of was obtained by extrapolation to high field of the term determined by Fourier analysis of unsaturated torque curves. This is closer to the result for single crystals than the other methods. The SPD method was used to analyse data recorded in high pulsed fields to determine the large values of for sintered Nd - Dy - Fe - B magnets with various compositions. There is an increase in that is linear in the Dy content.

High remanence (Sm, Zr)Fe7Nx+α-Fe nanocomposite magnets through exchange coupling

We have investigated the influence of α-Fe content on the magnetic properties of (Sm, Zr)Fe7Nx+α-Fe nanocomposite permanent magnet materials. As α-Fe content increases, the saturation magnetization and the remanence increase while the coercivity decreases monotonously. Also we confirmed the influence of microstructure on magnetic properties. Uniform and fine grain sizes of around 20 nm realized high remanence and high squareness of demagnetizing curve such as Br=9.9 kG, HcJ=9.1 kOe, Hk/HcJ=29.9%, and (BH)max=17.8 MGOe. These experimental results agree well with micromagnetic calculations by other researchers. Compaction-molded bonded magnet was prepared by magnetic powders with magnetic properties of Br=9.9 kG, HcJ=8.2 kOe, (BH)max=17.5 MGOe and 2 wt% of epoxy resin. Bonded magnet with a density of 5.91 g/cm3 showed high magnetic properties as follows: Br=7.6 kG, HcJ=8.4 kOe, and (BH)max=12.0 MGOe.

Maqnetic Properties And Phase Transfer Of SmFe/sub 2/And SmFe/sub 3/ Intermetallic comp ounds By Nitrogenation.

Magnetic properties and phase transfer of SmFe/sub 2/ and SmFe/sub 3/ compounds before and after nitrogenation are examined. It is found that SmFe/sub 2/ and SmFe/sub 3/ specimens show ferromagnetic properties with saturation magnetization of around 60 and 80 emu/g and Curie temperature of 425 degrees C and 410 degrees C, respectively. After nitrogenation, these compounds are thought to be decomposed into SmN and alpha Fe, considering X-ray diffraction and thermomagnetic analysis. It is assumed that the produced soft magnetic phase would deteriorate the magnetic properties of Sm rich Sm/sub 2/Fe/sub 17/N/sub x/ type magnets. >

High performance RFeCoZrB bonded magnets having low Nd content

The magnetic properties of resin bonded magnets made of rapidly quenched RFeCoZrB alloys with lower than stoichiometric Nd content were investigated. Two kinds of alloys were studied: NdFeCoZrB alloys and MM (misch metal)-based RFeCoZrB alloys. Isotropic resin bonded magnets with (BH)/sub max/ as high as 13 MGOe were obtained with the NdFeCoZrB alloys. For the MM-based magnets, a (BH)/sub m/ of 9.5 MGOe was obtained. Both magnets show good magnetizability and high loop squareness. >