Magnetic and magnetoelastic properties of antiferromagnet FeGe₂

The magnetic susceptibility $χ$ of single-crystal antiferromagnet $FeG e 2$ (⁠ $T N$ = 289 K) was measured in the temperature range from 4.2 to 300 K in a magnetic field H up to 40 kOe applied along the main crystallographic axes. For the antiferromagnetic (AFM) state at low temperatures, a strong increase in $χ$ is observed with increasing H applied along the [100] axis, which reaches saturation at $H≥ H 0∼$ 11 kOe. It is assumed that this behavior is associated with a field-induced change in the AFM domain structure, and the single-domain state is realized in a field above $H 0$ with the AFM axis perpendicular to the field direction. The study of $χ$ under the uniaxial $P a$ and uniform P pressures in a wide temperature range has revealed an anomalously large increase in $χ$ in AFM state with increasing uniaxial pressure for $P a||H||[100]$ at $H≪ H 0$⁠. The observed growth of $χ$ saturates at pressure $P a≥ P a∗≃1.5$ kbar and suggests the formation of the single-domain state for the above conditions. The values of uniform pressure effect on $χ$ was found to lie in the range $dln⁡χ/dP$ = − (2–3) Mbar^–1, being weakly dependent on the magnetic state and field direction. In addition, the uniform pressure effect on the transition temperature between two AFM structures in $FeG e 2$⁠, $T M≃263$ K, was found to be weak.