Regulation of phase transition and magnetocaloric effect by ferroelectric domains in FeRh/PMN-PT heterojunctions

Abstract

The narrow temperature span, ΔTspan, of first-order magnetocaloric materials is a serious problem that limits the application as refrigerants. Here we report tunable phase transition and magnetocaloric effect controlled by ferroelectric (FE) domains in FeRh films grown on (001)- and (011)-cut PMN-PT substrates. Adjacent two-step phase transition, and hence significantly broadened ΔTspan, has been achieved in FeRh films by utilizing the multi-domain structure of PMN-PT substrates. The results of aberration corrected (ac)-STEM, EELS and EDX analysis revealed that a 3~4 nm buffer layer with AB2O4-type spinel structure is naturally formed at the interface, which largely reduces the lattice mismatch between FeRh and PMN-PT and plays a key role for the successful growth of epitaxial (oriented) FeRh film on either (001)- or (011)-oriented PMN-PT. The switched FE domains by electric field govern the phase transition of FeRh films. As a result, regulated entropy change and refrigeration capacity in a wide temperature span have been achieved. On this basis, a feasible magnetic refrigeration cycle facilitated by electric field is designed. The present study provides an experimental basis for expanding the refrigeration temperature span by ferroelectric domain engineering, which is significant for promoting refrigeration application of first-order magnetocaloric materials particularly in micro-devices.