Induced magnetization at interfacial Cu atoms in epitaxial Fe/Co/Cu₃Au(001)

Full text: Induced magnetization has already been observed in some non-magnetic metals, as Rh or Pt, due to proximity effect with ferromagnetic films. X-ray magnetic circular dichroism (XMCD) measurements at Rh M2,3 edges show a significant magnetic polarization induced by Fe or Co ultrathin films grown on Rh(111) substrate [1]. Furthermore, Fe and Co ultrathin films grown on Rh(111) and Pt(111) present enhanced spin and orbital moments when compared to bulk materials [1]. However, Rh and Pt are close to satisfying the Stoner criterion for magnetism [2], and a ferromagnetic order is expected for ultrathin films [1]. Cu has a Stoner parameter of only 0.08, far away from the unit value required to fulfill the Stoner criterion, and is not expected to be magnetic [2]. Induced magnetic moment in Cu atoms has been previously observed only in Cu spacers in systems like Fe/Cu, Co/Cu or Co/Cu/Pt multilayers [3,4]. In this work, we investigate the induced magnetism in the interface between alternate Fe/Co monolayer films and a Cu₃Au(001) monocrystal. The Cu3Au(001) was prepared by sputtering (1500 eV) and annealing (850 K) cycles. Fe/Co samples were prepared by alternate evaporation of Fe and Co monoatomic layers (5 ML). The film structure and epitaxy were monitored by LEED and RHEED. XMCD measurements at Cu, Co and Fe L2,3 edges at 10 K and 310 K were performed at the PGM beamline at the Brazilian Synchrotron Light Laboratory (LNLS). A clear magnetic dichroism has been observed on Cu atoms in this system. As far as we know, this is the first time that an induced dichroism is observed on a Cu alloy. References: [1] A. Lehnert et al., Phys. Rev. B 82, 094409 (2010). [2] M. M. Sigalas and D. A. Papaconstantopoulos, Phys. Rev. B 50(11), 7255-7261 (1994). [3] G. A. Held et al., Z. Phys. B 100, 335 (1996). [4] J. Okabayashi et al., Sci. Rep. 7, 46132 (2017). (author)