Studies on the magnetoelastic and magnetocaloric properties of Yb < inf > 1-X < /inf > Mg < inf > x < /inf > MnO < inf > 3 < /inf > using neutron diffraction and magnetization measurements

Abstract

We report the magnetic ordering and magnetoelastic coupling of polycrystalline hexagonal Yb1-xMgxMnO3 (x = 0.00 and 0.05) compounds by using neutron diffraction measurements. The magnetocaloric properties of these Yb1-xMgxMnO3 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 TN1 ∼ 85 K (the Mn ordering temperature) due to the magnetoelastic effect. Also all the Mn-O bond distances display considerable variation at TN1. 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 (-ΔSM) is calculated from the magnetization curves measured for different temperatures. Values of maximum entropy change (-ΔSmaxM), the adiabatic temperature change (ΔTad) 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 -ΔSMvs. T curves for various fields fit into a single curve, implying the second-order phase transition.