Magnetic ordering of YPd2Si-type HoNi2Si and ErNi2Si compounds

Abstract

Magnetic properties of YPd2Si-type HoNi2Si and ErNi2Si were investigated via neutron diffraction and magnetisation measurements. HoNi2Si and ErNi2Si show ferromagnetic-like ordering at TC of 9K and 7K, respectively. The paramagnetic Weiss temperatures are 9K and 11K and the effective magnetic moments are 10.76μB/fu and 9.79μB/fu for HoNi2Si and ErNi2Si compounds, respectively. The HoNi2Si and ErNi2Si are soft ferromagnets with saturation magnetization of 8.1μB/fu and 7.5μB/fu, respectively at 2K and in field of 140kOe. The isothermal magnetic entropy change, ΔSm, has a maximum value of −15.6J/kg·K at 10K for HoNi2Si and −13.9J/kg·K at 6K for ErNi2Si for a field change of 50kOe.Neutron diffraction study in zero applied field shows mixed ferromagnetic-antiferromagnetic ordering of HoNi2Si at ~9K and its magnetic structure is a sum of a-axis ferromagnetic Fa, b-axis antiferromagnetic AFb and c-axis antiferrromagnetic AFc components of Pn′a21′={1, mx′/[1/2, 1/2, 1/2], 2y′/[0, 1/2, 0], mz/[1/2, 0, 1/2]} magnetic space group and propagation vector K0=[0, 0, 0]. The holmium magnetic moment reaches a value of 9.23(9)μB at 1.5K and the unit cell of HoNi2Si undergoes isotropic contraction around the temperature of magnetic transition.