VOLUME 85, NUMBER 2 PHYSICAL REVIEW LETTERS 10 JULY 2000 Layer-Resolved Magnetic Moments in Ni Pt Multilayers F. Wilhelm, P. Poulopoulos,* G. Ceballos, H. Wende, and K. Baberschke Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin-Dahlem, Germany P. Srivastava Department of Physics, Indian Institute of Technology (IIT), Hauz Khas, 110 016 New Delhi, India D. Benea and H. Ebert Institut für Physikalische Chemie, Ludwig Maximilians Universität München, Butenandtstrasse 5-13, D-81377 München, Germany M. Angelakeris and N. K. Flevaris Department of Physics, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece D. Niarchos Institute of Materials Science, NCSR-“Demokritos,” 15310 Athena, Greece A. Rogalev and N. B. Brookes European Synchrotron Radiation Facility (ESRF), B.P.220, 38043 Grenoble, France (Received 23 November 1999) The magnetic moments in NiPt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples’ magnetizations. X-ray mag- netic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically “dead” Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys. PACS numbers: 75.70.Cn, 75.25.+z, 75.30.Cr Magnetic multilayers constitute a new class of materi- als exhibiting a rich variety of novel effects related to the artificial structure, the large number of interfaces, and the confinement of electrons in ultrathin layers [1–3]. Un- derstanding the mechanisms governing these and related effects is crucial for designing materials with desirable properties. However, in the past the lack of experimental sensitivity in the monolayer (ML) limit was restricting our insight. It is only now that experiments on magnetic thin films and multilayers can provide complete and detailed in- formation to be compared with calculations [4]. In paral- lel, ab initio calculations allow one nowadays to study magnetism on an atomic scale. Satisfactory agreement be- tween theory and experiment can be achieved even for the magnetic anisotropy energy which is only a small fraction 10 26  of the total energy in solids; see, e.g., [5,6]. In this work we combine powerful experimental and ab initio theoretical techniques to give a complete, layer- resolved, picture of the magnetic moments in multi- layers. As a prototype system we select the NiPt one because (i) the interfaces between Ni and Pt in evaporated NiPt multilayers are sharp in the ML limit, as was shown by structural characterization via x-ray diffraction (XRD) and electron microscopy [7,8]. As evidence we show in Fig. 1 the u-2u XRD spectrum for a Ni 2 Pt 2 multilayer. The indices are numbers of ML in one multilayer period. The multilayer diffractions prove that the multilayer structure is present even for films with extremely thin (2 ML) Ni and Pt layers. That is, interdiffusion, if any, is strictly limited to the inter- face. (ii) NiPt multilayers are candidates for magneto- optic (MO) recording, since they show perpendicular magnetization at room temperature and a pronounced Kerr rotation maximum at the blue wavelength [7]. Both effects are strongly related to strain and hybridization at the NiPt interface. Although the properties of the NiPt FIG. 1. u-2u XRD spectrum for a Ni 2 Pt 2 multilayer. Despite the very thin Ni and Pt layers a small-angle multilayer and a high-angle first-order satellite diffraction are shown indicative of sharp interfaces. The Pt-buffer-layer diffraction and the solid solution diffraction from 111 and 200 are indicated. 0031-9007 00  85(2)  413(4)$15.00 © 2000 The American Physical Society 413