Magnetic properties and magnetocaloric effect in intermetallic compounds NdMn_2-xCo_xSi₂

Abstract

We report magnetic properties and magnetocaloric effect in intermetallic compounds NdMn_2-xCo_xSi₂ (x = 0.2, 0.4, 0.6, 0.8, and 1). dc magnetization study shows that these compounds undergo a ferromagnetic-like transition at around 45 K. Neutron diffraction study at 5 K for the x = 0.2 sample shows a canted-ferromagnetic state at lower temperature (5 K), and a collinear antiferromagnetic state at higher temperature (above ∼50 K). At 5 K, the Nd moments are aligned along the crystallographic c-axis and the Mn moments are canted to the c-axis. At higher temperatures (50, 100, 200, and 300 K), Nd sublattice does not order but Mn sublattice orders antiferromagnetically. A magnetocaloric effect (MCE) is found with a magnetic entropy change of 14.4 and 12.4 J kg⁻¹ K⁻¹ for the x = 0.2 and 0.4 samples, respectively, at 47.5 K under a field variation of 50 kOe. Various interesting phenomena such as metamagnetic transitions and domain wall pinning have been observed, and their role in obtaining a large MCE and an inverse MCE, respectively, has been brought out. The hysteresis (in magnetic field dependent dc magnetization study) reduces significantly at temperatures near and above the magnetic transition temperature (T_C), which makes these materials important for their practical applications in magnetic refrigeration around T_C.