Studies on the magnetoelastic and magnetocaloric properties of Yb1−xMgxMnO3 using neutron diffraction and magnetization measurements

Abstract

We report the magnetic ordering and magnetoelastic coupling of polycrystalline hexagonal Yb_1−xMg_xMnO₃ (x = 0.00 and 0.05) compounds by using neutron diffraction measurements. The magnetocaloric properties of these Yb_1−xMg_xMnO₃ compounds are also studied using magnetization measurements. The temperature dependence of the lattice parameters (a and c/a ratio) and unit cell volume V show anomalous behavior near T_N1 ∼ 85 K (the Mn ordering temperature) due to the magnetoelastic effect. Also all the Mn–O bond distances display considerable variation at T_N1. Isothermal magnetization curves measured near the Yb long range ordering temperatures indicate a field induced magnetic transition with applied field. The isothermal magnetic entropy change (−ΔS_M) is calculated from the magnetization curves measured for different temperatures. Values of maximum entropy change (−ΔS^max_M), the adiabatic temperature change (ΔT_ad) and the relative cooling power (RCP) for these compounds are found to be 3.02 ± 0.37 J mol⁻¹ K⁻¹, 8.6 ± 0.95 K and 41 ± 9 J mol⁻¹ for x = 0.00, and 2.63 ± 0.36 J mol⁻¹ K⁻¹, 9.06 ± 0.96 K and 40.0 ± 10 J mol⁻¹ for x = 0.05, respectively, for ΔH = 100 kOe. Rescaling of the −ΔS_M vs. T curves for various fields fit into a single curve, implying the second-order phase transition.