Magnetic properties and magnetocaloric effect of NdMn2-xCuxSi2 compounds

Structural and magnetic properties of NdMn(2-x)CuxSi(2) compounds (x=0-1.0) have been investigated by high intensity x-ray and resolution neutron diffraction (3-450 K), specific heat, 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. Two magnetic phase transitions have been found for NdMn(2-x)CuxSi(2) compounds with T-N for the antiferromagnetic ordering of Mn-sublatttice and T-C for the Nd-sublattice ferromagnetic ordering, respectively. T-C increases significantly with increasing Cu content from 36K at x = 0 to 100K at x - 1.0. Moreover, it is found that the order of magnetic phase transition around T-C also changes from first order at x < 0.6 to second order transition for x >= 0.6. The spontaneous magnetization found to decrease with the increase in Cu concentration which can be understood in the term of the dilution effect of Cu for Mn. The values of -Delta S-M around T-C decrease with increasing x from 27J kg(-1) K-1 for x = 0 to 0.5 J kg(-1) K-1 for x = 1.0 under 0-5 T field. Refinement of neutron diffraction patterns for x = 0.2 confirms the magnetic states detected by magnetic study and also indicates that the lattice constants a and c show a distinct variation around T-C. (C) 2014 AIP Publishing LLC.