O. Nashima

New magnetic material based on SmCo4B

The compound SmCo4B is a hard magnetic material; however, the saturation moment and the Curie temperature need to be increased for the compound to be a candidate for a permanent magnetic material. For this purpose, Fe substitution for the Co and Pr substitution for the Sm of SmCo4B have been attempted. In addition, the nitrogenation of SmCo2Fe2 is also attempted. The magnetic characteristics of SmCo2Fe2B have been investigated in a pulsed high magnetic field up to 350 kOe, and the data are compared with those of other related compounds investigated in this work. The compound with more Fe content, SmCo1.7Fe2.3B, has been successfully made, and TC=794 K and saturation moment Ms=81.4 emu/g at 300 K have been obtained. It is found that the Fe substitution does not decrease the uniaxial magnetic anisotropy. Heat treatments in nitrogen gas at 500 °C of SmCo2Fe2B have brought about significant increases of magnetization; however, the increase of TC is only about 20 K and the crystal volume is unchanged to within...

Exchange fields at rare-earth sites in Rn+1Co3n+5B2n (R=Gd and Dy) compounds

Spontaneous magnetization and paramagnetic susceptibility have been measured for the Rn+1Co3n+5B2n compounds with R=Y, Gd, and Dy and n=1, 2, and 3 in the temperature range from 4.2 up to 1000 K in fields up to 20 kOe. The data on the Gd system are analyzed based on the molecular field model. The exchange field at the Gd site from the Co sublattice is estimated. The averaged exchange field at T=0 K is estimated to be 101 T for n=1, 75T for n=2, and 56 T for n=3. Paramagnetic susceptibilities are fairly well expressed by the superposition of the Co- and the Gd-sublattice contributions. Other magnetic properties of the Y and the Gd system are also reported. Only magnetic data are given for the Dy system.

Magnetovolume effects of MnAs1−xSbx

Thermal expansion, high‐field magnetization, and susceptibility measurements have been made for MnAs0.7Sb0.3. The thermal expansion measurements show that the spontaneous magnetostriction is large and anisotropic below Tc. The spontaneous magnetostriction at 0 K is estimated to be 1.2×10−2 for a axis, −0.8×10−2 for c axis, and 1.6×10−2 for the volume. The spontaneous magnetization decreases sharply in the narrow temperature region below Tc=230 K. All the spontaneous magnetostrictions are found to be proportional to the square of spontaneous magnetization. The magnetization curves measured in a high field up to 40 T show the metamagnetic‐like transitions at temperatures above Tc, and they are almost perfectly reproduced by an equation H=A1σ+A2σ3+A3σ5, where H is the applied field and σ is the relative magnetization.

Magnetic properties of RCo3B2(R=rare earth) compounds

In order to investigate the crystalline electric field at R (R=rare earth) site and the induced magnetic moment at Co site in RCo3B2 compounds, high field magnetization process up to 15 T and paramagnetic susceptibility have been measured at various temperatures. It is found by analysis of the experimental data that (1) the crystal field parameter A20 is very large (∼−2000Ka0−2) and (2) significant magnetic moment (0.15–0.93μB) is induced at the Co site, in RCo3B2 compounds.

Magnetic anisotropy of Rn+1Co3n+5B2n (R=Y, La; n=1, 2, 3)

Abstract Magnetization curves have been measured at T = 4.2 K for field-aligned samples of compounds LaCo 4 B and Y n + 1 Co 3 n + 5 B 2 n with n = 1, 2 and 3, in a pulsed high magnetic field up to 35 T. Magnetocrystalline anisotropy constants K 1 have been estimated and discussed for the compounds mentioned above.

Anomalous magnetic properties of the compound SmCo3B2

Magnetization measurements for the compound SmCo3B2 have been performed on loose powder in magnetic fields to 5 T and in the temperature region from 4.2 to 60 K. A small saturation moment of 0.18 μB/SmCo3B2 at T=4.2 K and its variation with increasing temperature suggest ferrimagnetic ordering in SmCo3B2, which is explained as the effect of a higher order crystalline field coefficient. A magnetic first order transition occurs at T=43 K and metamagnetism occurs in the narrow temperature region between 43 and 47 K, for which some possible discussions are given.

Weak ferromagnetism in Cr1−xFexAs compound system

Magnetic measurements reveal that the compounds Cr1−xFexAs with 0.1 < x < 0.9 are weak itinerant electron ferromagnets although CrAs and FeAs compounds have a similar double spiral spin ordering.

Magnetic phase transition of MnAs1−xSbx

Abstract Magnetic properties and magnetovolume effects are investigated for MnAs 1− x Sb x , and all of the experimental data are found to be explained semi-quantitatively on the basis of the Bean-Rodbell model.

Neutron diffraction studies on Dy(Cu1−xNix)2Si2

Neutron powder diffraction studies have been made for Dy(Cu1−xNix)2Si2 with x=0, 0.06, and 0.1. The diffraction patterns of DyCu2Si2 are consistent with the reported magnetic structure [k=(1/2,0,1/2)], the Neel temperature (TN=10 K) and the Dy magnetic moment (8.2 μB). The diffraction patterns of Dy(Cu0.94Ni0.06)2Si2 and Dy(Cu0.9Ni0.1)2Si2 are interpreted by the same commensurate antiferromagnetic structures with k=(1/2,0,1/2). The Neel temperatures of Dy(Cu0.94Ni0.06)2Si2 and Dy(Cu0.9Ni0.1)2Si2 are determined to be 7.5 and 6.5 K, respectively. The magnetic moments are 6.5 μB/Dy in the Dy(Cu0.94Ni0.06)2Si2 and 6.0 μB/Dy in the Dy(Cu0.9Ni0.1)2Si2. The magnetic moment decreases as the Ni concentration increases, whereas the Dy moment determined by the Mossbauer spectroscopy increases as x increases. There is a strong diffuse peak at the (1/2 0 1/2) position of Dy(Cu0.94Ni0.1)2Si2 which implies the existence of some kinds of short range ordering of Dy moments. This fact suggests that the local crystalline el...