Transformations in the Gd5(Si1.95Ge2.05) alloy induced by the temperature and magnetic-field cycling through the first-order magnetic-martensitic phase transition

Temperature dependencies of the dc electrical resistivity, dc magnetization, and heat capacity of virgin Gd₅(Si_1.95Ge_2.05) samples and after they had been cycled through the first-order phase transition by varying temperature or magnetic field were studied. The virgin sample shows a transition from the low-temperature phase α to the high-temperature, low-resistance phase β'. After several temperature and/or magnetic field induced cycles of the Gd₅(Si_1.95Ge_2.05) alloy through the first-order phase transition, the α phase transforms to β'' where β'' is the high-resistance phase. The dc magnetization and zero magnetic field heat capacity data indicate that the temperature of the α<-->β'' phase transition is lower by ~2 K relative to α<-->β', while the electrical resistance shows ~7 K temperature difference. The observed phenomena are discussed based on the mechanism of the simultaneous magnetic/crystallographic phase transition in Gd₅(Si_xGe_4-x).