Magnetic and Magneto-Optic Properties of PtFe(001) and PtCo(OOl) Thin Films
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MAGNETIC AND MAGNETO-OPTIC PROPERTIES OF PtFe(001) AND PtCo(001) THIN FILMS Bruce M. Lairson, Mark R. Visokay, Robert Sinclair and Bruce M. Clemens Department of Materials Science and Engineering Stanford University, Stanford, CA 94305-2205
ABSTRACT We report on the magnetic and magneto-optical properties of PtFe and PtCo intermetallic thin films when they have the CuAu(I) tetragonal structure and their crystallographic c axis is oriented out of the film plane. These films possess large perpendicular magnetic anisotropy energies. We observe changes in the magneto-optic Kerr rotations of Pt-Fe and Pt-Co alloys associated with the formation of the uniaxial CuAu(I) crystal structure. In particular, we report the observation of up to 60% enhancement in the magneto-optic Kerr rotation for ordered, epitaxial PtFe intermetallic alloy over that of the random face centered cubic alloy. This enhancement is wavelength dependent, with a peak in the visible light range at 2.0 eV.
INTRODUCTION Thin films possessing perpendicular magnetic anisotropy are important for a number of applications, including magnetic recording. The Pt/Co and Pt/Fe alloy and multilayer systems have been studied extensively because they are found to possess perpendicular magnetic anisotropy when they are stacked along the [111] crystallographic direction, and because they have acceptable magneto-optic recording figures of merit for recording at short optical wavelengths. Here, we present magnetic and magneto-optic Kerr rotation results for multilayers based on a different kind of stacking, that of the naturally occurring superlattices PtFe and PtCo, consisting of atomic monolayers stacked along the [001] axis. These phases possess large magnetocrystalline anisotropy, approaching 20x10 6 ergs/cm 3 . They are also of interest in thin film form because of the large magnetooptic Kerr rotations available from PtCo and PtFe alloys and intermetallic compounds[l], their relatively large magnetizations (500-600emu/cm3), and their thermodynamic stability. The formation of these phases with the c axis oriented out of the film plane is accompanied by large perpendicular magnetic anisotropy and perpendicular remanent magnetization, as well as enhanced polar Kerr rotations at some wavelengths. The ordered PtFe and PtCo intermetallic compounds have Curie temperatures from 400 to 500'C, making thermomagnetic writing possible, although the transition temperature is higher than optimal. Alloying, for instance with Ni, produces CuAu(I) structure phases with lower transition temperatures.
SAMPLE PREPARATION Epitaxial multilayers were grown by sputtering onto epitaxial Pt(001) oriented seed layers. The seed layers were deposited onto polished single crystals of MgO(001) using a
Mat. Res. Soc. Symp. Proc. Vol. 313. ýý1993 Materials Research Society
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technique described elsewhere[2]. The equiatomic multilayers consisted of multiple bilayers of Pt/Fe and Pt/Co deposited at 100°C. This yielded epitaxial multilayers with the [001] cube axes out of plane for the FCC Pt a
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