Exchange biasing of permalloy films by MnxPt1-x:: Role of composition and microstructure

The interfacial coupling energy, Delta sigma for polycrystalline Ni0.8Fe0.2 (100 Angstrom)/MnxPt1-x(t Angstrom)/SiO2 bilayers, has been determined from wedge samples spanning a MnxPt1-x composition range 0.42 <x<0.76 and t similar to 350 Angstrom. Delta sigma exhibits a sharp peak of 0.1 erg/cm(2) at 51% Mn. We compare the magnetic and microstructural properties of two bilayer films, which have the same compositions of permalloy and MnxPt1-x: [Ni0.85Fe0.15 (100 Angstrom)/Mn0.49Pt0.51 (t Angstrom)]. In one case (normal structure), the epitaxial permalloy was grown first onto Pt/MgO(001), followed by 170 Angstrom of Mn0.49Pt0.51. In the other structure (inverted), a 350 Angstrom thick polycrystalline film of Mn0.49Pt0.51 was grown onto a SiO2 substrate, followed by permalloy. The structures exhibited very different exchange bias fields (32 versus 86 Oe) and Delta sigma values (0.021 versus 0.060 erg/cm(2)), respectively. Significant differences in texture, grain size, and Mn0.49Pt0.51 layer thickness for the two samples are reported. (C) 1998 American Institute of Physics.