Tuning of magnetic structure and its effect on magnetic properties in Co(Cr1–xMnx)2O4 (x = 0–0.3)

Abstract

We report here the magnetic properties of Co(Cr1–xMnx)2O4 (x = 0.00–0.30) through bulk-magnetization measurements and temperature variable neutron powder diffraction experiments. We have noticed the compensation temperature (Tcomp) and then the onset of negative magnetization at T = 60 K and 83 K only for Co(Cr0.73Mn0.27)2O4, i.e., x = 0.27, and Co(Cr0.70Mn0.30)2O4, i.e., x = 0.30 samples. Low temperature neutron diffraction experiments on these polycrystalline samples (i.e., x = 0.27 and 0.30) are performed to explore the understanding of observed negative magnetization, complex magnetic properties, and correlation between chemical and magnetic structures. A broad hump has been observed around the (111) Bragg reflection which gives the signature of diffuse scattering from short-range magnetic interactions coexisting with long range magnetic order below ordering temperature. The variation of bond lengths, bond angles, and magnetic moments with temperature is correlated, which clearly indicates magneto-elastic coupling around compensation temperature in these compounds. The presence of this magneto-elastic coupling results in the sign change of the magneto-caloric effect at compensation temperature.