Correlation of structure and magnetism of ultrathin Co films on Pd(001) prepared by thermal and pulsed laser deposition

Abstract

We present a combined experimental and theoretical analysis of the atomic structure and the magnetic properties of 1-and 2-monolayer ͑ML͒-thick Co films on Pd͑001͒ grown by thermal deposition ͑TD͒ and pulsed laser deposition ͑PLD͒. While surface x-ray diffraction measurements show that the geometric structures of the as-deposited samples differ depending on the deposition method ͑alloy formation for PLD versus epitaxial growth for TD͒, magneto-optic Kerr-effect loops indicate an in-plane easy magnetization axis independent of the preparation method. Annealing at 600 K induces a reorientation of the easy magnetization axis from in-plane to out of plane. This goes in parallel with substantial structural reorganization, leading to a Co/ Pd multilayer structure with a top Pd layer. In agreement with experiments, fully relativistic Kohn-Korringa-Rostoker calculations including experimentally derived structural relaxations and disorder predict in-plane magnetization for the as-grown samples and out-of-plane magnetization for the annealed 2 ML sample characterized by an ͑incomplete͒ Pd/ Co/ Pd/ Co/ Pd͑001͒ layer sequence. However, in-plane magnetization for the 1 ML Pd/ Co/ Pd͑001͒ sandwich is theoretically predicted. Our study emphasizes the decisive importance of structural order, relaxation, and interface contribution to the magnetic anisotropy energy.

Growth mode, magnetic and magneto-optical properties of pulsed-laser-deposited Au/Co/Au(111) trilayers

“…This fact arises from the several orders of magnitude higher instantaneous deposition rate during the laser pulse duration and from the increased kinetic energy of the ejected species (up to several eV) as compared with TD [4]. The second aspect is to potentially induce some intermixing at interfaces [5], which may be a drawback to reach certain physical properties depending on the smoothness of interfaces. Evidence of an increased tendency of intermixing at interfaces in structures grown by PLD versus TD has been given previously by X-ray diffraction [5], and it is generally thought to result from the energy carried by the atoms or ions evaporated from the target and heated upon further interaction with the laser in the plume [4].…”

“…The second aspect is to potentially induce some intermixing at interfaces [5], which may be a drawback to reach certain physical properties depending on the smoothness of interfaces. Evidence of an increased tendency of intermixing at interfaces in structures grown by PLD versus TD has been given previously by X-ray diffraction [5], and it is generally thought to result from the energy carried by the atoms or ions evaporated from the target and heated upon further interaction with the laser in the plume [4]. Here we report on the growth by PLD and the resulting magnetic and magneto-optical (MO) properties of epitaxial Au/Co/Au trilayers, motivated by the observed perpendicular magnetic anisotropy in TD grown [6] or electrodeposition (ED) [9] Co/Au(1 1 1) films capped with various materials.…”

Co monolayers and adatoms on Pd(100), Pd(111), and Pd(110): Anisotropy of magnetic properties

“…Note that the theoretical MAE of -0.18 meV given in Ref. 17 was obtained for a partially disordered Co monolayer simulating the growth conditions, so it cannot be directly compared to our results obtained for an ideal monolayer.…”

“…For example, the constant volume approximation yields z Co-Pd =1.70Å for a Co monolayer on Pd(100) while we took z Co-Pd =1.65Å instead, following the surface X-ray diffraction experiment of Meyerheim et al 17 For the other two surfaces we used the constant volume approximation distances, namely, z Co-Pd =1.96Å for Co on Pd (111) and z Co-Pd =1.20Å for Co on Pd(110). In the case of the (111) surface we can compare our distance with an EXAFS-derived experimental distance z Co-Pd =2.02Å (Ref.…”

No alloying in Fe deposited on Pd(001) at room temperature

“…Formation of the L1 0 structure most likely requires higher annealing temperatures, which were not applied in the present set of experiments to avoid extensive alloying of the substrate Pd crystal. Finally, it should be noted that support for this model comes from our very similar studies on the Co/ Pd͑001͒ interface, 28,37 showing the formation of the L1 0 -alloy structure ͓Pd/ Co/ Pd͑001͔͒ upon annealing the as-deposited nonalloyed sample to 620 K.…”