Magnetic properties of honeycomb spin lattice compounds Na2M2TeO6 (M = Co, Ni) and spin dimer compound Na2Cu2TeO6 single crystals by flux-growth

摘要

We report the single crystal growth, structural and magnetic properties of honeycomb spin-lattice compounds Na2M2TeO6 (M = Co, Ni) and spin dimer compound Na2Cu2TeO6. The single crystals of Na2M2TeO6 (M = Co, Ni, Cu) have been grown by the self-flux method, which is one of the good techniques to control the magnetic impurity, different crystalline phase, crystal morphology, crystal size and the crystal surface through the selection of a suitable self-flux. Crystal structure, magnetic and thermodynamics properties are examined using X-ray diffraction (XRD), magnetic susceptibility and heat capacity measurements, respectively. The single crystal XRD studies of Na2M2TeO6 (M = Co, Ni, Cu) show the purity and the high quality of grown single crystals. The measurements of magnetic susceptibility of Na2M2TeO6 show the distinct anisotropic behaviour of the prepared single crystals. The anisotropic behaviour and the complicated magnetic phase transitions observed arise from the distinct honeycomb planes constituted by MO6 octahedra in Na2M2TeO6 (M = Co, Ni) leading to the antiferromagnetic (AFM) interaction in the honeycomb planes. In the case of Na2Cu2TeO6 broad maximum occurring at 160 K is believed to arise from short-range one-dimensional antiferromagnetic correlations. The values of (effective magnetic moment) μeff. observed for Na2Co2TeO6, Na2Ni2TeO6 and Na2Cu2TeO6 are 5.42 μB, 3.17 μB and 1.96 μB respectively.