Field-induced magnetic structures in ErGa₂

Abstract

ErGa₂ crystallizes in the hexagonal A1B₂-type structure and shows a two-step magnetization process along the c-axis below T_N = 7 K. The compound has a magnetic structure with a wavevector of $\text{Q}{}_1\text{=}\text{1}\text{2b}\text{∗}$ at H = O, and for the intermediate field range it has a structure with $\text{Q}{}_1\text{,Q}{}_2\text{=}\text{1}\text{2a}\text{∗}$, $\text{Q}{}_3\text{= −}\text{1}\text{2a}\text{∗ +}\text{1}\text{2b}\text{∗}$ and Q₀ = 0. The magnetization process is studied in terms of a wave-like molecular field H_m(u,v,w,) = Σ_qλ_m(q)<J(q)#62cos(2πqr_uvw acting on Er at point r_uvw. The analysis involves wavevector-dependent molecular field coefficients λ_m(q) with q = 0, Q₁, Q₂ and Q₃ and one crystal field coefficient B₂⁰. The dipole field due to the dipole-dipole interaction is also involved. Calculations give a reasonable fit with the magnetization data with λ(0) = −1.84 kOe; λ_m(Q₁) = λ_m(Q₂) = λ_m(Q₃) = 0.68 kOeandB₂⁰ = − 0.48 K. A possible explanation for the appearance of the magnetic structure in the intermediate field range is presented.