Ni-Co合金の強磁性的擧動について(第2報)

Abstract

With about sixty, annealed, nickel-cobaelt alloys covering the whole composition range, magnetization curves for magnetic fields up to 900 oersteds were measured ballistically at ordinary temperatures. It is shown that magnetization curves have the three types corresponding to different structures involved in this alloy system, that is, γ (face-centered cubic) and ε (hexagonal close-packed) solid solutions and the mixture of these phases. Magnetization curves of γ-phase alloys show high susceptibilities, and saturate at relatively low fields (atmost 700 Oe). The magnetization of an alloy containing about 3 or 10 percent cobalt was found to saturate at the lowest field (about 30 Oe). ε-phase alloys have low suscetibilities and high saturation fields, and two-phase alloys show behaviors intermediate between γ-phase and ε-phase alloys. The magnetization for constant magnetic field and the initial and the maximum magnetic susceptibility vs. composition curves show discontinuitic at 68 and 77 percent cobalt. These two compositions were shown to be the boundaries of the two-phase range, contrary to _??_ prevailing opinion that the range was quite narrow near 70 percent cobalt. The relation between the saturation magnetization and composition of γ-phase alloys was found to be well expressed by two straight lines of slightly different slopes, which connected at the middle of the range. The straight line for high cobalt contents may, practically, be extended up to pure cobalt. Both initial and maximum magnetic susceptibilities show three sharp peaks in the compostion range below about 30 percent cobalt. Provided that the first, comparatively low, peak is neglected, this mode of variation is quite similar to that of the contribution of the continuous rotation of spontaneous magnetization to the initial susceptibility. This means that the said contribution to the initial susceptibility may bs superior to, other contributions in materials of low anisotropy constant.