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

TL;DR

This study explores how hydrostatic pressure influences the magneto-structural transition and induces exchange bias effects in a Fe-doped MnNiGe alloy, revealing pressure-dependent magnetic and magnetocaloric properties.

Contribution

It demonstrates pressure-tuned control of phase transition and the novel pressure-induced exchange bias effect in Mn$_{0.85}$Fe$_{0.15}$NiGe alloy, which was not previously reported.

Findings

Pressure shifts martensitic phase transition to lower temperatures.

Magnetocaloric effect decreases with increasing pressure.

Exchange bias effect appears under external hydrostatic pressure.

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.