Magnetostructural properties and electric transport in Mn48+xCr3-xNi38Sn11 (x = 0, 1) ribbons: Mn/Ni ratio versus Cr doping

We report the structural, electrical and magnetic properties of Cr substituted Mn48+xCr3-xNi38Sn11 (x = 0 and 1) Heusler ribbons synthesised by melt spinning of the arc-melted bulk alloy. Composition analysis employing EDAX reveals same Ni and Sn concentrations with difference in the Mn/Cr ratio in both the ribbons. Mn48Cr3Ni38Sn11 ribbons have pure cubic-austenite phase whereas Mn49Cr2Ni38Sn11 show a mixture of the dominant cubic-austenite with traces of the orthorhombic-martensitic phase as confirmed by X-ray analysis. Ribbons having higher Cr content show (i) pure cubic austenite structure (L21 type) at room temperature (ii) canonical paramagnetic-ferromagnetic transition in the austenite phase and (iii) metallic temperature dependence of resistivity. Small decrease in the Cr content produces dramatic changes in the structure-property profile. Hence ribbons having lower Cr content show (i) a mixture of cubic and orthorhombic phases, (ii) paramagnetic-ferromagnetic transition in the austenite phase above the room temperature which is followed by strongly hysteretic martensitic transition and (iii) metal-like temperature dependence of resistivity followed by typical martensitic resistivity and re-entrant metallic behaviour in the lowest temperature region. AC susceptibility measurements show absence of a spin glass like behaviour in Mn48Cr3Ni38Sn11 while the lower Cr variant demonstrates nearly ideal spin glass like characteristics. The high sensitivity of structure-property correlation towards small compositional variations is attributed to the twin effect of Cr substitution at Mn sites and the Mn/Ni ratio.