  We report a giant, ~22%, electroresistance modulation for a metallic alloy
above room temperature. It is achieved by a small electric field of 2 kV/cm via
piezoelectric strain-mediated magnetoelectric coupling and the resulting
magnetic phase transition in epitaxial FeRh/BaTiO3 heterostructures. This work
presents detailed experimental evidence for an isothermal magnetic phase
transition driven by tetragonality modulation in FeRh thin films, which is in
contrast to the large volume expansion in the conventional temperature-driven
magnetic phase transition in FeRh. Moreover, all the experimental results in
this work illustrate FeRh as a mixed-phase model system well similar to
phase-separated colossal magnetoresistance systems with phase instability
therein.
