High-field magnetization of Er₂(Co_0.4Fe_0.6)₁₇

The quasibinary intermetallic compound Er₂(Co_0.4Fe_0.6)₁₇ (hexagonal Th₂Ni₁₇-type structure) is a ferrimagnet with T_C = 1170 K and M_s = 21 μ_B/f.u. The magnetic anisotropy is of easy-axis type at low temperatures, changing to an easy-plane anisotropy near room temperature. In the present work, the magnetization was measured in fields up to 60 T along the easy c axis. A first-order transition was observed at 47 T with a magnetization jump of 9 μ_B/f.u. Er2(Co0.4Fe0.6)17 is an ideal model system for high-field experiments since the observed transition admits an unambiguous quantitative interpretation. This is because the compound also undergoes a first-order magnetization process at 1.5 T enabling an independent direct determination of the anisotropy constants. A further advantage is the smallness of the 3d contribution to the anisotropy, which can be neglected altogether. With these parameters the observed high-field magnetization curve was successfully modeled.