Dependence of martensite transformation temperature on magnetic field in Ni2MnGa and Ni2MnGa0.95In0.05 single crystals

The shift of martensite transformation temperatures with magnetic field is an essential parameter for magnetic shape memory effect as well as for magnetocalorics. We compare the dependence of martensite transformation temperature on magnetic field in Ni2MnGa and Ni2MnGa0.95In0.05 single crystals. Choosing the stoichiometric and isoelectronic compound enables to observe the effect of In alloying free from the influence of off-stoichiometry. The martensite start temperature, Ms, decreases several kelvins in low magnetic fields (< 1 T). In high field (> 2 T), Ms increases with the magnetic field and the Ms(H) dependence is about linear with the slope of 0.26 K/T (Ni2MnGa) and 0.36 K/T (Ni2MnGa0.95In0.05). Modest 1.25 at% indium alloying decreases not only transformation temperature Ms by about 100 K but also considerably decreases the latent heat of martensite transformation from 1.99 kJ/kg (Ni2MnGa) to 0.29 kJ/kg (Ni2MnGa0.95In0.05) determined from Clausius-Clapeyron equation. The latent heat of premartensitic transformation also decreases, approximately five times.