Torque magnetometry study of magnetically ordered state and spin reorientation in the quasi-one-dimensional $S=1/2$ Heisenberg antiferromagnet CuSb$_2$O$_6$

TL;DR

This study uses torque magnetometry and ESR spectroscopy to investigate magnetic anisotropy, spin reorientation, and anisotropic exchange interactions in the quasi-one-dimensional $S=1/2$ Heisenberg antiferromagnet CuSb$_2$O$_6$, revealing complex temperature-dependent magnetic behavior.

Contribution

It provides new experimental evidence of anisotropic exchange interactions and spin-lattice coupling in CuSb$_2$O$_6$, highlighting the complex magnetic anisotropy and spin reorientation phenomena.

Findings

Macroscopic magnetic axes rotate with temperature above 50 K

ESR linewidth indicates presence of anisotropic exchange interactions

Below 8 K, the system exhibits long-range antiferromagnetic order with spin reorientation

Abstract

We present an experimental study of macroscopic and microscopic magnetic anisotropy of a spin tetramer system \cso using torque magnetometry and ESR spectroscopy. Large rotation of macroscopic magnetic axes with temperature observed from torque magnetometry agrees reasonably well with the rotation of the $\mathbf{g}$ tensor above $T \gtrsim 50$~K. Below 50~K, the $\mathbf{g}$ tensor is temperature independent, while macroscopic magnetic axes continue to rotate. Additionally, the susceptibility anisotropy has a temperature dependence which cannot be reconciled with the isotropic Heisenberg model of interactions between spins. ESR linewidth analysis shows that anisotropic exchange interaction must be present in \csos. These findings strongly support the presence of anisotropic exchange interactions in the Hamiltonian of the studied system. Below $T_N=8$~K, the system enters a long - range antiferromagnetically ordered state with easy axis along the $<\bar{1} 0 1>^*$ direction. Small but significant rotation of magnetic axes is also observed in the antiferromagnetically ordered state suggesting strong spin-lattice coupling in this system.