Abstract
The influence of addition of Co on the structural and magnetic properties of MnSb was investigated. The compound formed in the NiAs-type hexagonal structure. Addition of Co to MnSb causes changes in both the lattice parameters. It was observed, from magnetization measurements, that both Curie temperature and saturation magnetization decrease from those of MnSb. The spin-polarized density of states (DOS) calculations revealed that the intermetallic compound favors ferromagnetic ground state even after as much as 0.25 atom of Co per formula unit of MnSb. Charge transfer takes place from the interstitial Co-atom to minority spin band of Mn-atom resulting in an increase in the DOS compared to MnSb at the Fermi level. MnSbCo0.25 exhibits a negative magnetocaloric effect with the largest change in the entropy value, ΔSm = 2.5 J. kg-1. K-1 (for a change in magnetic field from 0 to 5 T), across the second order phase transition at 292 K. The change in the value of magnetic entropy is low around the phase transition and might be due to the small magnetic moment of Mn-atom.
Highlights
Magnetic refrigeration has gained significant interest in recent years, as a clean alternative to the conventional cooling methods employing JT effect.1 In general, magnetic refrigeration requires the combination of a large magnetic field and a material with a significant magnetocaloric effect (MCE).The change in magnetic entropy mainly depends on whether the material undergoes first order phase transition (FOPT: due to either structural phase transition or magnetic phase transition) or second-order phase transition (SOPT: order-disorder transition).2 In some materials exhibiting FOPT, the large change in entropy is due to the coexistence of both structural and magnetic phase transitions
The available density of states at the Fermi level is low in MnSbCo0.25 though the addition of Co causes the DOS in MnSbCo0.25 to increase compared to MnSb
Two phase transitions were observed at 152 K and 292 K from the M(T) curves. These transition values are different from the reported values on slowly cooled materials
Summary
Magnetic refrigeration has gained significant interest in recent years, as a clean alternative to the conventional cooling methods employing JT effect.1 In general, magnetic refrigeration requires the combination of a large magnetic field and a material with a significant magnetocaloric effect (MCE).The change in magnetic entropy mainly depends on whether the material undergoes first order phase transition (FOPT: due to either structural phase transition or magnetic phase transition) or second-order phase transition (SOPT: order-disorder transition).2 In some materials exhibiting FOPT, the large change in entropy is due to the coexistence of both structural and magnetic phase transitions (from one magnetic phase to another magnetic phase). Addition of Co to MnSb causes an increase of the a value and decrease of the c value.7 Both Curie temperature (TC) and saturation magnetization (MS) of MnSb decrease with the addition of Co. The fact that the TC of MnSbCo0.25 is 325 K, close to RT, provides an opportunity to investigate magnetocaloric effect (MCE) in this compound.7 In the present article, magnetocaloric studies on
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