UC Berkeley

The separate effects of strain and film thickness on the antiferromagnetic-to-ferromagnetic phase transition temperature of FeRh thin films by both experiment and density functional calculations were determined. Strain was introduced by epitaxial growth onto MgO, SrTiO3, and KTaO3 substrates. Film thicknesses below 15 nm substantially suppress the transition temperature, T, to below room temperature in unstrained films. For strained films, tensile/compressive strain decreases/increases T, respectively. KTaO3 (001) substrates produce sufficient compressive strain to increase the transition temperature of 10 nm FeRh films above room temperature, which is useful for many proposed applications previously limited by the stabilization of the ferromagnetic state at small thicknesses. These results demonstrate that a judicious use of film thickness and substrate can be used to manipulate FeRh's transition temperature over a ∼200 K range.