Anomalous magnetic and magnetocaloric properties of Er₂Ni ₁₇

Intermetallic compound Er₂Ni₁₇ crystallizes in the hexagonal Th₂Ni₁₇-type structure with the space group P6₃/mmc and lattice parameters a ≤ b ≤ 8.282 and c ≤ 8.033 . The magnetization measurements show that it is ferrimagnetic below its magnetic ordering temperature of 150 K. The temperature variation of zero-field-cooled magnetization in a field of 200 Oe shows the compensation point at about 63 K. On the other hand, the field-cooled magnetization in low fields is found to be negative at low temperatures. The compensation temperature is found to shift to low temperatures with an increase in the field. These variations are explained on the basis of the two sublattice model. The intersublattice molecular field coefficient (n_RT) and the intersublattice exchange coupling constant (J_RT) have been calculated using the high-field free-powder method. The n_RT and J_RT values are found to be 1.4 Tf.u./μ_B and 5.2 K, respectively. The magnetocaloric effect has been measured in terms of the isothermal magnetic entropy change, using the magnetization isotherms. The maximum entropy change is about 2 J kg^-1 K^-1 for a field of 50 kOe.