Structure analysis using XRD refinement for replacement of copper (Cu) with manganese (Mn) in NdMn 2 Si 2 compound
In magnetic materials, a change in the degrees of freedom of the spins induces thermal effects can be used in refrigeration technology. Simultaneous occurrence of changes in structure bring an effect on magnetocaloric effect (MCE) and thus influence the magnetic refrigeration operation. Structural and magnetic properties of NdMn 2-x Cu x Si 2 compounds (x = 0 - 1.0) have been investigated by refinement of room temperature X-ray diffraction (XRD), DC magnetization, and differential scanning calorimetry measurements. Substitution of Cu for Mn leads to an increase in the lattice parameter a but a decrease in c at room temperature. Furthermore, increasing the Cu concentration in NdMn 2-x Cu x Si 2 compounds lead to increase the secondary structure (impurity) as indicated the additional of peak in XRD measurement. Curie Temperature (T C ) increases significantly with increasing Cu content from 36K at x = 0 to 100K at x = 1.0. Two magnetic phase transitions have been found in NdMn 2-x Cu x Si 2 compounds refer to NdMn 1.8 Cu 0.2 Si 2 compound as reference to Neel Temperature (T N ) for the antiferromagnetic ordering of Mn-sublatttice and T C for the Nd-sublattice ferromagnetic ordering. The values of magnetic entropy change, -ΔS M around T C decrease from 27J kg -1 K -1 for x = 0 to 1.5J kg -1 K -1 for x = 1.0 under 0-5 T field with increasing of Cu concentration, respectively.