Magnetocaloric effect in spin-glass-like GdCu4Mn compound

Abstract

Materials based on Gd with magnetic frustration may have high magnetocaloric application potential. GdCu4Mn crystallizes in hexagonal CaCu5-type structure with space group P6/mmm (no. 191, Pearson symbol: hP6). Lattice parameters for the polycrystalline sample are equal to a = 5.114(3) Å and c = 4.151(4)Å. Due to structural disorder, namely random distribution of Cu and Mn atoms on 2c and 3g positions, a spin-glass-like behavior is observed in this material at low temperatures. In addition to the standard measurements of DC magnetization and AC magnetic susceptibility, the spin-glass state was confirmed by the memory effect and relaxation behavior. The absence of clear anomalies in the temperature dependencies of specific heat and electrical resistance suggests the lack of long-range magnetic order. For a change in magnetic field from 0 to 5 T, maximum values of the isothermal magnetic entropy change (ΔSm), temperature averaged entropy change (TEC(5)), relative cooling power (RCP), and adiabatic temperature change (ΔTad) at ∼50 K are equal to −1.3(1) J/(kg K), 1.2(1) J/(kg K), 125(1) J/kg, and 0.5(1) K, respectively.