Hydrogenation effect on the hysteresis properties of rapidly quenched Nd–Ho–Fe–Co–B alloys

► Hysteresis properties of rapidly quenched (RQ) Nd–Fe–B alloy and its hydride. ► Magnetic anisotropy and a grain size are the key factors affecting the coercivity. ► Existing magnetic phase with high local coercivity in RQ alloys at T = 4.2 K. The hydrogenation effect on the hysteresis properties of rapidly quenched (RQ) (Nd 0.55Ho 0.45) 2.7(Fe 0.8Co 0.2) 14B 1.2 compound obtained by melt-spinning is studied. A comparative study of RQ alloy and its hydride (Nd 0.55Ho 0.45) 2.7(Fe 0.8Co 0.2) 14B 1.2H 2.5 has shown that hydrogenation resulted in the increase of magnetization without significant effect on the Curie temperature. In contrast to hydrogen-free alloy having a maximum on the H c( T) curve, the H c of the hydrogen-charged compound increased monotonously with decreasing temperature. Among the factors affecting H c in hydrogenated sample are the increase of the grain size of the crystalline phase and the decrease of both the iron and the rare earth contributions to the magnetocrystalline anisotropy. High-field hysteretic distortions of the magnetization/demagnetization curves of RQ and RQ + hydrogen samples are observed at 4.2 K in fields up to 90 kOe indicating the existence of a magnetic phase with very high local coercivity.