Two-step antiferromagnetic transition and moderate triangular frustration in Li2Co(WO4)2

I. Panneer Muthuselvam; R. Sankar; A. V. Ushakov; G. Narsinga Rao; Sergey V. Streltsov; F. C. Chou

paper

Two-step antiferromagnetic transition and moderate triangular frustration in Li2Co(WO4)2

arXiv:1411.6075

Abstract

We present a detailed investigation of the magnetic properties of the spin- $\frac{3}{2}$ system Li $_{2}$ Co(WO $_{4}$ ) $_{2}$ by means of magnetic susceptibility and specific heat. Our experimental results show that in Li $_{2}$ Co(WO $_{4}$ ) $_{2}$ a short-range antiferromagnetic (AFM) correlations appear near $χ$ $_{ma x}$ $\sim$ 11 K and two successive long-range AFM phase transitions are observed at T $_{N 1}$ $\sim$ 9 K and T $_{N 2}$ $\sim$ 7 K. The frustration factor, $∣$ $Θ$ $∣$ /T $_{N 1}$ $\sim$ 3, indicates that the system is moderately frustrated, which is identifiable by the broken triangular symmetry within both $ab$ - and $b c$ -planes for the triclinic crystal structure. The magnetic isotherm at temperatures below T $_{N 2}$ shows a field-induced spin-flop transition, and a complete H-T phase diagram for the two-step AFM system is mapped. $A b$ ~ $ini t i o$ band structure calculations suggest that the strongest exchange coupling does not correspond to the shortest Co-Co distance along the $a$ -axis, but rather along the diagonal direction through a Co-O-W-O-Co super-superexchange path within the $b c$ -plane

7 Pages, 10 Figures