A facile in situ reduction route for preparation of spinel CoCr2O4 polycrystalline nanosheets and their magnetic properties

Abstract

Considerable efforts have been exerted on the controllable synthesis of nanomagnetic materials due to their size- and morphology-dependent properties. Herein, a facile ethylene glycol in situ reduction strategy has been successfully employed in the preparation of CoCr₂O₄ nanosheets. X-ray diffraction patterns showed that the products have the cubic spinel structure. The electron microscopy analysis revealed that the obtained CoCr₂O₄ nanosheets consisted of nanoparticles with the diameters of 20–30 nm. Experiments proved that the volume ratio of ethylene glycol to water was crucial for the final morphology. The magnetization studies demonstrated that besides the long-range ferrimagnetic order below the Curie temperature (T_C = 86 K), the sample exhibited two low-symmetry ordered states including the spiral magnetic order at T_S = 20 K and the magnetic lock-in transition at T_L = 13 K. The crystallinity- and size-dependent magnetic properties were also investigated. The temperature dependence of the specific heat revealed both phase transition at T_C = 90 K and T_S = 20 K, in line with the magnetic results.