Induced triplet transitions by the effect of antiferromagnetic (Sm) substitution and investigations on structural, magnetic, magnetocaloric properties of Mn1-xSmxCoGe heulser alloys

Abstract

We investigate on structure, surface morphology, magnetic and magnetocaloric properties of Mn1-xSmxCoGe (x = 0, 0.2, 0.4 and 0.6) alloys. MnCoGe crystalizes in TiNiSn type doublet orthorhombic (O1, O2) structure [parent compound (x = 0)] changes into a mixed phase of orthorhombic and hexagonal structures while doped with Sm and hexagonal phase is enhanced with increase of Sm content. Lattice parameters and phase fractions are reported. Surface morphological images of SEM shows Sm embedded on MnCoGe. The partial substitution of Sm at Mn site in Mn1-xSmxCoGe leads to a wide transition from the ferromagnetic–paramagnetic [FM-PM] around room temperature. However, some anomaly is observed for x = 0.6 due to induced triplet transitions such as Curie (TC-FM-PM transition appears at 270 K), Martensitic (TM-FM-Martensitic ~ 200 K) and Neel transitions (TN antiferromagnetic-paramagnetic [AFM-PM] transition at 30 K). The Arrott plots confirm the order of transitions. The Curie and Neel’s transitions are explored from isothermal magnetic measurements. The change in magnetic entropy (ΔSM) [−23 Jkg-1K−1 (x = 0) to −0.045 Jkg-1K−1 (x = 0.6)] are decreased for Sm doped (x = 0.2, 0.4 and 0.6) samples. These observations provide constructive information that will be highly benefit applications for this class of magneto response materials which is used for magnetic refrigeration technology near room temperature.