High-field planar magnetization processes in Tm2Fe14B

Abstract

Magnetization curves for Tm2Fe14B, at 4.2 and 78 K, have been calculated for external magnetic fields up to 200 T, applied in the a-b plane, by using a first-principles model of the Tm-Fe exchange and crystal-field interactions. It has been shown that at 4.2 K there is a field-induced planar fan-magnetic structure for moderate fields applied along the (100) direction. In this applied field range, the Fe-sublattice magnetization is not parallel to the applied field direction. First-order magnetization processes are predicted at 4.2 K, at critical fields of mu 0Hcr1=47.9 T (with a corresponding change in magnetization of Delta M=6.90 mu B FU-1) and mu 0Hcr2=73.5 T ( Delta M=9.94 mu B FU-1) for (100) and mu 0Hcr1=59.8 T ( Delta M=7.89 mu B FU-1) for (110), respectively. At 78 K, a ferri to ferromagnetic transition has been identified in both the (100) and (110) magnetization curves. Initially, the Tm moments are canted about the negative Fe-sublattice magnetization direction. When the external applied field increases, the magnitudes of the Tm moments decrease and vanish at the critical field, mu 0Hff=62.2 T, which is exactly equal to the exchange field acting on the Tm3+ ions. With further increases in applied field, the magnitudes of the Tm moments, which are now canted along the positive Fe direction, increase again.