Ground state and magnetic transitions of the orthorhombic antiferromagnet CaCo$_2$TeO$_6$

Abstract

We report the systematic synthesis, crystal structure, magnetization, and powder neutron diffraction of single crystalline and polycrystalline CaCo$_2$TeO$_6$ samples. CaCo$_2$TeO$_6$ crystallizes in an orthorhombic structure with $Pnma$ space group, featuring chains of edge-shared CoO$_6$ octahedra arranged in a honeycomb pattern. Two antiferromagnetic transitions are observed at $T$$_{N1}$ = 14.4 K and $T$$_{N2}$ = 16.2 K, corresponding to two long-range magnetic orders with propagation vectors of $\bf{k}$$_1$ = (0, 0, 0) and $\bf{k}$$_2$ = (0.125, 0, 0.25), respectively. The ground state is determined as a canted up-up-down-down zigzag spin configuration along the $c$ axis, wherein the magnetic moments of Co1 and Co2 ions are 3.4(1) and 2.1(1)$\mu$$_B$, respectively. Successive spin-flop transitions appear with the increasing magnetic field applied along the easy axis ($c$ axis), accompanied by depression of the antiferromagnetic orders and enhancement of residual magnetic entropy. The field-induced spin-disordered state suggests that CaCo$_2$TeO$_6$ may be an ideal candidate for studying frustrated magnetism.