Electric control of magnetic properties in epitaxially grown FeRh/MgO/PMN-PT heterostructures.

• The insertion of an MgO buffer layer significantly reduces the large lattice mismatch between FeRh and PMN-PT. • The FeRh(001) film is epitaxially grown on the ferroelectric PMN-PT(001) substrate. • The epitaxial FeRh(001) film displays multi-step hysteresis loops at various field orientations at 350 K. • The butterfly shape of coercivity vs electric field indicates a strain-mediated magnetoelectric coupling. • The transition temperature and the magnetization are enhanced and reduced in the remnant polarization state, respectively. We epitaxially grew the metamagnetic FeRh films on ferroelectric PMN-PT(001) substrates and investigated the electric control of magnetic properties. An MgO buffer layer is inserted to reduce the considerably large lattice mismatch of 5.44% between FeRh and PMN-PT, leading to a nice epitaxial growth with a relationship of FeRh[110](001)||MgO[100](001)||PMN-PT[100](001). The as-grown FeRh film shows a typical antiferromagnetic-to-ferromagnetic phase transition by means of varying the temperature. Because a growth-induced uniaxial magnetic anisotropy is superimposed on the in-plane four-fold magnetocrystalline anisotropy, the epitaxial FeRh film displays different kinds of multi-step hysteresis loops at various field orientations. An electric field applied on the PMN-PT substrate can remarkably increase the coercivity of FeRh film, which presents a butterfly type shape, indicating a strain-mediated magnetoelectric coupling. Because of the inhibitory effect of the remnant compressive strain on the phase transition, the critical transition temperature and the magnetization are obviously enhanced and reduced, respectively, after removing the electric effect. [ABSTRACT FROM AUTHOR]