Hydrostatic pressure tuned magneto-structural transition and occurrence of pressure induced exchange bias effect in Mn$_{0.85}$Fe$_{0.15}$NiGe alloy

Abstract

Magnetic and magneto-functional behavior of a Fe-doped MnNiGe alloy with nominal composition Mn$_{0.85}$Fe$_{0.15}$NiGe have been investigated in ambient as well as in high pressure condition. The alloy undergoes first order martensitic phase transition (MPT) around 200 K and also shows large conventional magnetocaloric effect (MCE) ($\Delta S$ $\sim$ -21 J/kg-K for magnetic field ($H$) changing from 0-50 kOe) around the transition in ambient condition. Application of external hydrostatic pressure ($P$) results a shift in MPT towards the lower temperature and a clear decrease in the saturation moment of the alloy at 5 K. The peak value of MCE is also found to decrease with increasing external $P$ ($\sim$ 18 J/kg-K decrease in $\Delta S$ has been observed for $P$ = 12.5 kbar). The most interesting observation is the occurance of exchange bias effect (EBE) on application of external $P$. The competing ferromagnetic and antiferromagnetic interaction in presence of external $P$ plays the pivotal role towards the observation of $P$ induced EBE.