Eiji Tatsumoto

Origin of Magnetic Anisotropy of Iron Films Evaporated at Oblique Incidence

Detailed electron microscopic investigations confirmed that the shape anisotropies of the columnar grains grown in iron films evaporated at oblique incidence, which are parallel and perpendicular to the columnar grain axis, are principally responsible for both of the anisotropy fields H k (1) and H k (2) analyzed from torque measurements, respectively. Fiber textures found by X-ray diffraction were of the types of {111} and {100} perpendicular to the columnar grain axis, having minor contribution to H k (1) and H k (2), but appearing to have some connection with their rapid increase with increasing angle of oblique incidence.

Temperature Dependence of the Magnetostriction Constants in Iron and Silicon Iron

The magnetostriction constants λ 100 and λ 111 of Fe, 1.08 and 3.83% Si-Fe have been measured by using single crystals at temperatures below Curie point down to liquid air temperature with two newly designed apparatuses. In iron, λ 100 has a minimum around 400°K, while λ 111 monotonously decreases in numeral with increasing temperature. Addition of silicon to iron has a tendency to make the minimum in λ 100 disappear and to decrease λ 111 numerically at any temperature, retaining the similar monotonous variation with temperature. Several existing theories have been applied to account for the experimental results, but no theory appears to be successful in interpreting them.

Pressure Effect of Curie Point of CoS2 and Ferromagnetic Properties of Co(SxSe1-x)2

The change of the Curie point of CoS 2 under hydrostatic pressure up to 5.3 kbar was investigated, and the value of Δ T c / Δ P was obtained to be -0.86 deg·kbar -1 . The linear compressibility of FeS 2 , having approximately the same crystal structure with CoS 2 , was measured, and the value of (1/ l ) ( Δ l / Δ p ) was given as 2.31×10 -7 bar -1 at 296°K. The relation between the change of the Curie point and the interatomic distance was obtained from the both results. This result was applied to an explanation of the ferromagnetic property of Co(S x Se 1- x ) 2 , and the exchange interaction of this system was discussed. An iso-volume magnetic phase diagram of this system was illustrated.

Effect of Hydrostatic Pressure on the Magnetocrystalline Anisotropy constant K1 in Si-Fe and Ni

Variation of the anisotropy constant K 1 with hydrostatic pressure was determined on 1.08 wt. % Si-Fe and Ni from torque measurements under pressures up to about 5 kbar at 77, 195, 238 and 291 K. The pressure coefficient at absolute zero, (1/ K 1 (0))( Δ K 1 (0)/ Δ p ), was estimated by extrapolation as -2.1×10 -5 bar -1 for the Si-Fe and -1.4×10 -5 bar -1 for Ni. The temperature dependence of the anisotropy constant at constant volume, K 1 V , deduced with (1/ K 1 )( Δ K 1 / Δ p ) at all temperature appears to obey the ninth power of the magnetization for the Si-Fe.