Interplay of magnetic order and ferroelasticity in the spin-orbit coupled antiferromagnet K$_2$ReCl$_6$

TL;DR

This study investigates the coupling between magnetic order and ferroelastic structural transitions in K$_2$ReCl$_6$, revealing how magnetic fields influence domain structures and phase behavior in this antiferromagnetic material.

Contribution

It provides detailed insights into the interplay between magnetic and structural phase transitions, including domain reorientation and magnetic field effects, in K$_2$ReCl$_6$.

Findings

Magnetic fields can reorient ferroelastic domains in K$_2$ReCl$_6$.

Domain structures are linked to magnetic and structural phase transitions.

Heating and cooling cycles restore initial domain configurations.

Abstract

The magnetic and structural phase transitions occurring in K$_2$ReCl$_6$ were studied by macroscopic and microscopic techniques. Structural phase transitions associated with rotations of the ReCl$_6$ octahedra lower the symmetry from cubic to monoclinic, form ferroelastic domains, and are visible in susceptibility, specific heat and thermal expansion measurements. In the antiferromagnetically ordered state slightly below $T_{\rm N}$=12\,K these domains can be rearranged by a magnetic field inducing a relative elongation of the polydomain crystal parallel to the field of 0.6\%. At zero field the magnetic structure in K$_2$ReCl$_6$ does not exhibit a weak ferromagnetic component, but at large magnetic field a distinct magnetic structure with a finite weak ferromagnetic component is stabilized. High magnetic fields rearrange the domains in the crystal to align the weak ferromagnetic moment parallel to the field. The altered domain structure with the crystal elongation is abruptly suppressed at lower temperature but persists upon heating to well above $T_{\rm N}$. However, heating above the lowest structural phase transition and successive cooling restore the initial shape.