Hydrostatic pressure induced giant enhancement of entropy change as driven by structural transition in Mn0.9Fe0.2Ni0.9Ge0.93Si0.07

Abstract

The magnetostructural transition (MST) can be tuned close to room temperature for an isostructurally alloyed (MnNiGe)1−x(Fe2Ge)x (x = 0.1) compound by partially substituting a small amount of Si for Ge (7 at. %). In this study, the effect of hydrostatic pressure (p) on MST is investigated. In comparison to purely magnetically induced phase transition, pressure initiates structural transition more abruptly, which results in an increase in the isothermal entropy change by a factor of 2 from −Δs = 25.6 (p = 0) to 45.6 J/kg K (p = 190 MPa) for a magnetic field change of 2 T. Since the direct assessment of the adiabatic temperature change, ΔTad, is difficult due to the large volume change and subsequent structural breakdown at MST, an indirect method has been employed to estimate ΔTad.