Eiichi Hirota

Magnetic Properties of (Cr1-xFex)O2

The solubility limit of Fe-ion in CrO2 and the properties of (Cr1-xFex)O2 were examined. Added Fe-ions dissolve into CrO2 and form an oxide of (Cr1-2x4+Crx5+Fex3+)O2, up to the x-value of about 0.06. The Tc increases from 116°C for the pure CrO2 to about 155°C with an Fe-addition of x=0.06. The magnetic moments of Fe3+ and Cr5+ couple in anti-parallel way to that of Cr4+.

Mn-Zn-Ferrites with Low Loss Property and High Initial Permeability

The effects of the addition of CaO and GeO2 in iron excess Mn-Zn-ferrites were investigated for improving the high frequency loss property. The µQ value of 8×104 with µ of 700 at 1 Mc/s was obtained. The low loss property is attributed to its high resistivity caused by the addition of CaO and GeO2, followed by the domain wall stabilization by an induced anisotropy.

Coercive force of new Cu‐substituted samarium cobalt alloys

It was found that sintered alloys having a composition of approximately z=8 in Sm(Co0.85Fe0.05Cu0.10)z exhibit a high coercive force on the order of 10 kOe, for 5–10‐μm average grain size. Magnetization and demagnetization curves showed that the coercive force is controlled by a nucleation process. Attempts were made to achieve a high density without serious grain growth by means of high‐pressure isostatic compaction and hot pressing, resulting in 96% of the density and 7‐μm average grain size. With this approach, Br=10.3kG, IHc=10.2 kOe, and a maximum energy product of 22.0 MG Oe were achieved.

Anomalous Magnetization Processes at Low Temperatures in Compositionally Modulated Co/Mn Thin Films

Compositionally modulated Co/Mn thin films with layer thickness ranging from 7-70 A were prepared by UHV evaporation. The artificial periodicity was confirmed by small-angle X-ray diffraction. Magnetization of the CMF was found to decrease below a certain transition temperature and anomalous magnetization processes were observed at low temperatures.