Investigation of composition-induced strain effect in FexPt1−x films grown on different substrates

Different composition FexPt1−x films were fabricated on three typical single crystal substrates (MgO, KTaO3, and SrTiO3), and the composition-induced strain evolution of FexPt1−x films was systematically investigated. The study showed that different Fe compositions in Fe-Pt films resulted in different strain status and crystallographic textures, and thus influenced the magnetic properties. Under the tensile strain between the Fe-Pt and (MgO, KTaO3, and SrTiO3) substrates, Fe-Pt films preferred to form ordered Fe-Pt (001) texture. Decrease of the Fe atom concentration caused the Fe-Pt films to be further relaxed, and an obvious increase of lattice constant c. Moreover, with reducing the mismatch between Fe-Pt and substrate from MgO to KTaO3 and SrTiO3, the strain status of Fe-Pt films changed from completely strained to partially relaxed. The perpendicular anisotropy of Fe55Pt45 films grown on STO was larger than that grown on MgO and KTO, which was attributed to better epitaxial quality of the FePt (001) texture induced by less lattice mismatch.