Mn x Pt 1−x : A new exchange bias material for Permalloy

We report exchange biasing of Permalloy in as-grown ${\mathrm{Mn}}_x{\mathrm{Pt}}_{\text{1−x}}$ /Permalloy structures grown by coevaporation in ultra-high vacuum. Polycrystalline and epitaxial structures with $x$ between 0.35 and 0.75 were studied. X-ray diffraction confirms the presence of chemical ordering in the ${\mathrm{Mn}}_x{\mathrm{Pt}}_{\text{1−x}}$ films (grown at 200 °C) in as-grown polycrystalline and epitaxial structures. An interfacial coupling energy of 0.032 ${\mathrm{erg/cm}}^2$ is found for structures where the ${\mathrm{Mn}}_x{\mathrm{Pt}}_{\text{1−x}}$ $\text{(x=0.56)}$ is grown at 200 °C onto epitaxial Permalloy (001). Polycrystalline structures have a smaller (0.027 ${\mathrm{erg/cm}}^2$ ) interfacial coupling energy. No exchange bias is observed for films with $\text{x≲0.4}$ . The blocking temperature, for a sample with $\text{x=0.56}$ , is >500 K.