Comparing magnetostructural transitions in Ni50Mn18.75Cu6.25Ga25 and Ni49.80Mn34.66In15.54 Heusler alloys

The crystal structure, magnetic and transport properties, including resistivity and thermopower, of Ni50Mn18.75Cu6.25Ga25 and Ni49.80Mn34.66In15.54 Heusler alloys were studied in the (10-400) K temperature interval. We show that their physical properties are remarkably different, thereby pointing to different origin of their magnetostructural transition (MST). A Seebeck coefficient (S) was found to pass minimum of about -20 μV/K in respect of temperature for both compounds. It was shown that MST observed for both compounds results in jump-like changes in S for Ga-based compound and jump in resistivity of about 20 and 200 μΩ cm for Ga and In -based compounds, respectively. The combined analyzes of the present results with that from literature show that the density of states at the Fermi level does not change strongly at the MST in the case of Ni-Mn-In alloys as compared to that of Ni-Mn-Ga