Crossover from antiferromagnetic to ferromagnetic ordering in the semi-Heusler alloys Cu_1-xNi_xMnSb with increasing Ni concentration

Abstract

The magnetic properties and transition from an antiferromagnetic (AFM) to a ferromagnetic (FM) state in semi-Heusler alloys Cu_1-xNi_xMnSb, with x < 0.3 have been investigated in detail by dc magnetization, neutron diffraction, and neutron depolarization. We observe that for x < 0.05, the system Cu_1-xNi_xMnSb is mainly in the AFM state. In the region 0.05 ≤ x ≤ 0.2, with decrease in temperature, there is a transition from a paramagnetic to a FM state, and below ∼50 K, both AFM and FM phases coexist. With an increase in Ni substitution, the FM phase grows at the expense of the AFM phase, and for x > 0.2, the system fully transforms to the FM phase. Based on the results obtained, we have performed a quantitative analysis of both magnetic phases and propose a magnetic phase diagram for the Cu_1-xNi_xMnSb series in the region x < 0.3. Our study gives a microscopic understanding of the observed crossover from the AFM to FM ordering in the studied semi-Heusler alloys Cu_1-xNi_xMnSb.