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

TLDR

The authors demonstrate exchange biasing of Permalloy by co‑evaporating MnxPt1−x (x = 0.35–0.75) onto it in ultra‑high vacuum. They fabricated polycrystalline and epitaxial bilayers, studying the resulting structures at 200 °C to assess chemical ordering and interfacial coupling. X‑ray diffraction confirms chemical ordering, with interfacial coupling energies of 0.032 erg cm⁻² for epitaxial x = 0.56 and 0.027 erg cm⁻² for polycrystalline films; no bias appears for x ≲ 0.4, and the blocking temperature exceeds 500 K for x = 0.56.

Abstract

We report exchange biasing of Permalloy in as-grown MnxPt1−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 MnxPt1−x films (grown at 200 °C) in as-grown polycrystalline and epitaxial structures. An interfacial coupling energy of 0.032 erg/cm2 is found for structures where the MnxPt1−x (x=0.56) is grown at 200 °C onto epitaxial Permalloy (001). Polycrystalline structures have a smaller (0.027 erg/cm2) interfacial coupling energy. No exchange bias is observed for films with x≲0.4. The blocking temperature, for a sample with x=0.56, is >500 K.