Low temperature kinetic properties and structure of Ni50+xMn25-x+yGa25-y alloys with shape memory

We present results of kinetic coefficient experiments and structure studies in Ni50+xMn25-x+yGa25-y alloys at low temperatures. The magnetic, galvanomagnetic and electrical properties were measured in the temperature range from 2 to 80 K and in magnetic fields of up to 15 T. Two types of samples were investigated: cast samples with a grain size of about 100–500 μm and quenched samples with a grain size of about 300–500 nm. We find that the deviation from the stoichiometric composition leads to an increase of the structural and magnetic disorder and, hence, to changes in the low temperature kinetic properties. Similar effects are observed as the result of a quench treatment.