Irrecoverable and Recoverable Resistivity Resulting From the First Order Magnetic-Structural Phase Transition in Gd $_5$(Si $_x$Ge$_{1-x}$)$_4$

An irreversible change in resistivity occurs in Gd
$_5$
(Si
$_x$
Ge
$_{1-x}$
)
$_4$
at the first-order phase transformation each time the material is cycled through its transition. This results in a progressive increase in resistivity each time the material is cycled through the transition and returned to its initial conditions of temperature and magnetic field. The effect of a first-order magnetic/structural phase transition on the resistivity of a material, and its recovery by annealing have not been reported before, and consequently, there has been no theoretical analysis of the effect until now. We postulate that if the material is held at an elevated temperature, the resistivity recovers and recovery time decreases with temperature. A model has been developed to explain the recovery in resistivity when the sample is held at elevated temperatures over a period of time and this has been verified experimentally.