Magnetic and magnetoelastic properties of antiferromagnet FeGe2

Abstract

The magnetic susceptibility χ of single-crystal antiferromagnet FeGe₂ (T_N = 289 К) 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 ≥ H₀ ∼ 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 H₀ 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_а ║H ║ [100] at H ≪ H₀ . 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 dlnχ /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 FeGe₂ , T_M ≃263 K, was found to be weak.