Structural and magnetic studies of Co1-xNixCr2O4 (0 ≤ x ≤ 1)

Abstract

We have investigated the structural, magnetic, and thermal transport properties of Co 1 - x Ni x Cr 2 O 4 (0 ≤ x ≤ 1) to check the evolution of structural and magnetic properties upon the introduction of the Jahn-Teller active ion Ni 2 +. The x ≤ 0.95 samples can be indexed with a cubic lattice with the space group Fd3m, whereas the x = 0.98 sample undergoes a cubic-tetragonal structural transition, and the x > 0.98 samples belong to a tetragonal lattice with the space group I41-amd at room temperature. All these samples undergo a paramagnetic-ferrimagnetic transition at T C. A spiral ferrimagnetic ordering at T S is suppressed when the amount of Ni is increased, and the abnormal magnetization at T S for the x = 0.6 and 0.8 samples is not pronounced. The measurements of magnetic hysteresis reveal that the x = 0.4 and 0.6 samples possess a rather large coercivity H C compared with the x = 0 and 1 samples. Specifically, the x = 0.4 and 0.6 samples undergo a short-range antiferromagnetic transition above T C. The magnetic properties of the Ni-doped samples can be understood in terms of the magnetic structure model consisting of longitudinal and transverse magnetic sublattices.