Magneto-optical spectroscopy as a structure- and chemical-order sensitive probe

Abstract

We use the ex-situ technique of magneto-optical spectroscopy to characterize MBE-grown Co, Co-Pt, and evaporated Co-Ni films and show that subtle changes in the structural and chemical order as well as changes in the crystallographic properties can substantially affect the magneto-optical spectra. These can be viewed as a sensitive probe of the spin-polarized electronic structure of a magnetic material, which in turn is strongly structure dependent. In particular, we discuss the effect of the crystallographic phase on the spectra of 1000 angstrom thick fcc and hcp Co and fcc and hcp Co82Ni18 films in the photon energy range 08 - 5.5 eV. In Co1-xPtx alloys, of compositions x ≈ 0.75 and ≈ 0.5, large changes in the magneto-optical spectra are observed if chemical ordering is induced either by annealing below the disorder-order transition temperature or by direct growth near the ordering temperature. Other examples are the discovery of a new chemically ordered, hexagonal Co-Pt phase at the composition x ≈ 0.25 and an unprecedented large Kerr effect in the chemically ordered Fe1Pt1 (L10) phase.