Effect of Composition and Thickness on the Perpendicular Magnetic Anisotropy of (Co/Pd) Multilayers

Abstract

Magnetic materials with perpendicular magnetic anisotropy (PMA) have wide-ranging applications in magnetic recording and sensing devices. Multilayers comprised of ferromagnetic and non-magnetic metals (FM–NM) are interesting materials, as their magnetic anisotropy depends strongly on composition and growth parameters. In this context, (Co/Pd) multilayers have gained huge interest recently due to their robustness and tunable PMA. Here, we report a systematic study of the effect of composition on the magnetic anisotropy of (Co/Pd) multilayers grown by Direct Current (DC) magnetron sputtering. Four different series of (Co/Pd)×10 multilayers with different thicknesses of Co and Pd were examined. Vibrating sample magnetometery was used to determine the magnetic anisotropy of these films. X-ray diffraction and transmission electron microscopy experiments were performed to understand the structural morphology of the films. Our results showed that (Co/Pd)×10 multilayers exhibit PMA when the Co to Pd ratio is less than or equal to 1 and the thickness of Co layers is not more than 5 Å. Maximum effective anisotropy energy is shown by the films with a Co to Pd ratio of 1/3.

Observation of magnetic skyrmions in unpatterned symmetric multilayers at room temperature and zero magnetic field

“…To extract the perpendicular magnetic anisotropy, we used , which gives ≈ 0.06 MJ·m −3 . In a recent work, effective perpendicular anisotropy obtained for Co/Pd multilayes, similar values of PMA were obtained when the Pd layer is thicker than 0.9 nm 40 , 41 . We varied the magnetization saturation M s and magnetic anisotropy to understand the impact of these properties on the skyrmions stability considering a weak Dzyaloshinskii-Moriya below D = 0.8 mJ·m −2 .…”

Hydrogen tunes magnetic anisotropy by affecting local hybridization at the interface of a ferromagnet with nonmagnetic metals

“…We first investigated magnetic anisotropy at a pristine Co/Pd interface and further used these results as a reference to understand the origin of magnetic anisotropy changes after hydrogen insertion. In accordance with previous experimental data [32], our calculations showed that Co/Pd trilayers exhibit pronounced magnetocrystalline anisotropy (MCA) with −1.82 mJ/m 2 energy favoring the perpendicular orientation of magnetic moments. The magnetic moment on Co atoms is found to be in the range of 1.76-1.86 μ B , while adjacent Pd also acquires a weak magnetization corresponding to 0.28 μ B per atom, which decays fast with decreasing proximity to the interfacial Co layers [see Fig.…”

“…Increasing the number of Co layers diminishes the absolute value of MAE, causing anisotropy reorientation in thicker films, as observed experimentally [32]. The MCA contribution does not show any significant dependence on the number of Co layers, varying in the range of −1.75 to −1.85 mJ/m 2 (see Fig.…”

“…The calculated Co/Pd model was composed of 4 Co layers sandwiched between 14 Pd layers at both sides. In accordance with experimental data, we assumed an epitaxial growth of fcc Co on an [111] Pd substrate [32]. The in-plane lattice constant a of the supercell was constrained to bulk fcc Pd, a = 3.871 Å.…”

“…While the assumption of epitaxial growth is an appealing theoretical idealization, real Co films show some deviations from perfect epitaxial growth [32,39]. The substantial lattice mismatch may cause an introduction of interfacial dislocations to reduce the stress in interior Co planes.…”