Incommensurate-commensurate magnetic phase transition in the double tungstate Li2Co(WO4)2

TL;DR

This study investigates the magnetic phase transitions in Li2Co(WO4)2, revealing incommensurate and commensurate magnetic states through experimental and theoretical methods, with detailed insights into magnetic ordering and structure.

Contribution

The paper provides the first detailed experimental and theoretical analysis of the incommensurate-commensurate magnetic phase transition in Li2Co(WO4)2.

Findings

Two magnetic transitions at 9.4 K and 7.4 K observed.

Incommensurate magnetic state with temperature-dependent wave vector.

Magnetic structure refined with Co2+ moment of 2.8 μB.

Abstract

Magnetic susceptibility, specific heat, and neutron powder diffraction measurements have been performed on polycrystalline Li2Co(WO4)2 samples. Under zero magnetic field, two successive magnetic transitions at TN1 ~ 9.4 K and TN2 ~ 7.4 K are observed. The magnetic ordering temperatures gradually decrease as the magnetic field increases. Neutron diffraction reveals that Li2Co(WO4)2 enters an incommensurate magnetic state with a temperature dependent k between TN1 and TN2. The magnetic propagation vector locks-in to a commensurate value k = (1/2, 1/4, 1/4) below TN2. The antiferromagnetic structure is refined at 1.7 K with Co2+ magnetic moment 2.8(1) uB, consistent with our first-principles calculations.