Showing papers by "Shoichi Kume published in 1968"

Possible Existence of Dense Ferrimagnetic Perovskite Allotropic Form of Yttrium Iron Garnet

Abstract: Mixed oxides with the same chemical composition as yttrium iron garnet (YIG) were maintained at 900°C and 20 kbars for 30 min. X-ray diffraction showed that the product was single-phase. Since the diffraction pattern could be indexed as a structure similar to yttrium ortho-ferrite, YFeO3, the product was considered to be a deformed type of perovskite. Subsequently, the lattice constants were calculated to be a= 5.27, b= 5.57, and c= 7.59 A. Both measured and calculated densities were about 6% greater than those of YIG. This material, therefore, can be called a dense allotropic form of YIG. Ferrimagnetism was observed in this phase; the Curie temperature and the magnetic moment at room temperature were estimated to be 625° C and 63 emu/g, respectively. This dense form converted to YIG on heating at 900° C for 4 hr in air. The transformation of YIG to a dense form at high pressures is inconsistent with the results reported by Marezio et al. Some possible reasons for this discrepancy are discussed.

Demagnetization of Unstable Remanent Magnetization by Application of Pressure

Abstract: Summary Ferromagnetic minerals with ‘stable’ and ‘unstable’ components of remanent magnetization were subjected to hydrostatic compressions of up to 10 kbar. It was observed that the ‘unstable’ remanence was completely demagnetized by the application of pressure while the ‘stable’ remanence remained almost unchanged. The result indicates the possibility of utilizing high pressures in magnetic cleaning.