Magnetic Properties of Textured CoPd Nanocrystalline Thin Films

Abstract

CoPd is an important nanomaterial for magnetic and magneto-optic storage of information. In this work, CoPd alloyed thin films are grown via radio frequency magnetron sputtering on silicon, glass and polyimide substrates in a vacuum chamber with base pressure of 5 x 10(-8) mbar. The films are nanocrystalline with grain size between 4 and 80 nm. The magnetic properties of thoroughly textured CoPd alloyed thin films are compared to random polycrystalline ones. Magnetization hysteresis loops recorded under fields up to 12 kOe via a home-made magneto-optic Kerr-effect magnetometer reveal strong tendency for perpendicular magnetic anisotropy for the textured film. This anisotropy leads to the formation of well-defined stripe or labyrinthine ferromagnetic domains with the local spins oriented perpendicular to the film plane. The domain patterns and the hysteresis loops are simulated with micromagnetic calculations. Finally, an induced magnetic moment of 0.44 microB/atom is measured for Pd via X-ray magnetic circular dichroism and it is separated into spin and orbital magnetic moment contributions.

Magnetism of CoPd self-organized alloy clusters on Au(111)

“…In the thick Co 0.5 Pd 0.5 film, the Pd spin moment is 0.4 l B , comparable to the one obtained earlier in similar alloy films. 21 Figure 3 shows XMCD magnetization loops at the Co L 3 edge for the three samples at grazing and normal light incidence for various temperatures. From the shape of the loops at 4 K, one deduces that the easy magnetization axis is perpendicular to the surface for all samples.…”

Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

“…Pd h −n Ag h = 0.92 [67], (n Pd h = 1.27 [68], and n Ag h = 0.35 [69]), and the experimental XAS spectra of a Pd film and Ag, we estimated A wl /n h = 5.18(4) eV/holes, whereby n h = 0.85 (5) in Pd, which we assume to be also valid for the CoPd NPs. The smaller number of holes in CoPd than in metallic Pd (n Pd h = 1.27) reflects the hybridization of the 4d band in Pd with the 3d band in Co.…”

“…[91]) have been systematically found in Co-Pd systems [5,63,64]. However, the enhancement in very thin Pd layers, like the [Co/0.8 nm Pd] multilayers [63], or in 0.4 ML Co 0.5 Pd 0.5 nanoclusters on Au(111) [58], is at least two times smaller than in Co 1−x Pd x much thicker films [5,58,64] or bulk alloys (Table IV) [65,92]. The low Pd moment in the Co 0.5 Pd 0.5 nanoclusters on Au has been attributed to the stretching of the alloy to epitaxial conditions on Au (111) that reduces the Pd moment.…”

“…In particular, extensive works have been driven towards the ability to stabilize a magnetic easy axis perpendic-* jrubin@unizar.es ular to the substrate plane, which is central to magneto-optical storage and perpendicular magnetic media [5][6][7]. In this context, the research on bimetallic magnetic nanoparticles (NPs) of 3d ferromagnets and heavy metals has attracted much attention as they offer new possibilities to tune the material performance aiming to control the magnetic anisotropy energy (MAE) [8,9].…”

“…In particular, Co 1−x Pd x alloy films and Co/Pd multilayers show perpendicular magnetic anisotropy (PMA) and they have been extensively studied in order to understand the origin of its PMA. PMA has been reported in a variety of combinations of Co and Pd in the form of thin film alloys [5,11,12] and thin film multilayers [13]. The origin of PMA in Co/Pd multilayers has been attributed mainly to magnetic interface anisotropy [14], while in Co-Pd film alloys, PMA has been explained by both anisotropic strain and short range ordering of the Co atoms in the Pd matrix [15].…”