Magnetic structure and interlayer exchange coupling in spring magnets—studied via nuclear resonant scattering T. Klein a, ⁎ , R. Röhlsberger b , O. Crisan a,c , K. Schlage a , E. Burkel a a Institut für Physik, Universität Rostock, August-Bebel-Str. 55, 18055 Rostock, Germany b Deutsches Elektronen Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany c National Institute for Materials Physics, PO Box MG-7, 77125 Bucharest, Romania Received 19 October 2005; received in revised form 2 December 2005; accepted 9 March 2006 Available online 24 May 2006 Abstract Magnetic properties of FePt/Ag/Fe and FePt/Pd/Fe layer systems, prepared by magnetron sputtering, were investigated using the nuclear resonant forward scattering of synchrotron radiation. This technique allows the accurate determination of magnetic hyperfine field orientations by using an extremely thin 57 Fe probe layer suitably embedded within the soft magnetic layer. From an evaluation of these measurements within a one-dimensional micromagnetic model, the interlayer exchange coupling constants between the magnetically hard (FePt) and soft (Fe) layers were determined as function of the Ag and Pd interlayer thickness. The interlayer thickness dependence of the bilinear coupling constants provides evidence for the superposition of Ruderman–Kittel–Kasuya–Yoshida coupling and a magnetostatic interaction between the magnetic layers. © 2006 Elsevier B.V. All rights reserved. PACS: 75.70.-i; 61.10.-i; 75.25.+z; 76.80.+y Keywords: Exchange spring effect; Interlayer exchange coupling; Micromagnetic simulation; Nuclear resonant forward scattering The discovery of antiferromagnetic coupling between magnetic layers separated by a non-magnetic spacer layer (NM) [1] has initiated intense experimental and theoretical research in this field. Shortly after, it was observed that the intrinsic interlayer exchange coupling is oscillating between the ferro and antiferromagnetic state depending on the spacer thickness [2]. This coupling is often called the Ruderman– Kittel–Kasuya–Yoshida (RKKY) or quantum-well coupling [3]. Extrinsic mechanisms such as magnetostatic interactions caused by structural roughness for instance may also result in a ferro- and antiferromagnetic coupling between magnetic films, i.e. Nèel or orange peel coupling [4,5]. Much research has been devoted to soft magnetic layer systems such as Fe/NM/Fe or Co/NM/Co for detailed studies of the intrinsic RKKY-like mechanisms of the interlayer exchange coupling (IEC). In contrast, investigations of the IEC between soft and hard magnetic layers are relatively scarce. In the case of polycrys- talline FePt films, as in our samples, the magnetization is always non-saturated in the remanent case. Due to the more or less randomly oriented moments of the grains, the magnetic anisotropy fluctuates, resulting in stronger stray fields at the surface that substantially influence the magnetostatic interac- tion. The present paper focuses on the influence of the particular magnetic structure of the hard magnetic layer on the IEC of hard and soft magnetic layers separated by a non-magnetic spacer layer. Polycrystalline hard magnetic Fe 50 Pt 50 films, where the c- axes of the L1 0 structured crystallites are in-plane, and soft magnetic Fe layers (polycrystalline structure) separated by wedge shaped Ag and Pd spacer layers (slope: S max = 3.3 nm/ cm) were deposited on super-polished Si substrates using magnetron sputtering (Ar atmosphere p =1×10 − 2 mbar) in high vacuum (base pressure p =3×10 − 7 mbar). The hard magnetic FePt films are produced by co-deposition of Fe and Pt and then annealed in high vacuum at T = 500° for 15 min to form the L1 0 phase. A coercive field of 0.8 T at room temperature was determined via magneto-optic Kerr effect (MOKE) measure- ments. In order to avoid oxidation, 3 nm of Ag were deposited Thin Solid Films 515 (2006) 2531 – 2534 www.elsevier.com/locate/tsf ⁎ Corresponding author. E-mail address: klein@physik1.uni-rostock.de (T. Klein). 0040-6090/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2006.03.035