Neutron as a probe to study magnetization reversal in a spinel compound, CoCr_1.9Fe_0.1O₄

Abstract

Neutron depolarization and neutron diffraction techniques have been employed to investigate the origin of magnetization reversal in CoCr_1.9Fe_0.1O₄ spinel compound. The spinel compound crystallizes in a face centered cubic (space group: Fd-3m) structure where Co²⁺ and (Cr/Fe)³⁺ ions occupy the tetrahedral 8a and octahedral 16d sites, respectively. The temperature dependent magnetization curves for magnetic fields ≤ 1 kOe show a magnetization reversal below the compensation temperature (Tcomp ∼ 40 K). The neutron depolarization measurements infer that the average magnetization of each domain becomes negligibly small at the TComp. Temperature dependent neutron diffraction study, a microscopic tool to understand sublattice magnetization, infers an antiparallel coupling between the tetrahedral (Co) and octahedral (Cr/Fe) site moments with ordered magnetic moments of −3.1(1) and 1.0(1) μB, respectively, at 30 K. Our neutron diffraction study also reveals that the unequal growth of the antiferromagnetically coupled tetrahedral and octahedral site moments across the TComp plays an important role in realizing the magnetization reversal in this spinel compound.