Magnetocaloric effect and martensitic transition in Ni50Mn36−xCoxSn14

Highlights: • The general e/a dependence of TM lose effectiveness for Ni50Mn36–xCoxSn14. • Metamagnetic transition of Ni50Mn34Co2Sn14 occurs under 3.8 T at 277 K. • Ni50Mn34Co2Sn14 exhibits a large magnetocaloric effect. -- Abstract: The structural, magnetic and martensitic transition properties are systematically investigated for Ni50Mn36−xCoxSn14 (x = 0, 1, 2, and 3) alloys. X-ray diffraction reveals that all the compounds are in the cubic phase with the L21-type Heusler structure at room temperature. Temperature dependent magnetization indicates that the Curie temperatures of austenitic phases are almost unchanged with the substitution of Co for Mn. However, the martensitic transition temperatures firstly increase and then decrease with Co content increasing, which is different from the general dependency on the value of valence electrons per atom (e/a). The reason could be that the main driving force of martensitic transition for Ni50Mn36−xCoxSn14 is the hybridization between Ni and excess Mn rather than the value of e/a. Due to the strong coupling between magnetism and structure, Ni50Mn34Co2Sn14 exhibits a large magnetocaloric effect, thereby making it a good candidate for magnetic refrigeration materials