Magnetocrystalline anisotropy of small CoPt binary alloy metal clusters: interplay between structure, chemical compositi
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Magnetocrystalline anisotropy of small CoPt binary alloy metal clusters: interplay between structure, chemical composition, and spin-orbit coupling ˜ J. L. Ricardo-Ch´avez · M. Munoz-Navia · P. Ruiz-D´ıaz
Received: 31 March 2020 / Accepted: 21 May 2020 © Springer Nature B.V. 2020
M. Mu˜noz-Navia Universidad de La Ci´enega del Estado de Michoac´an de Ocampo, Avenida Universidad 3000, Col. Lomas de la Universidad, Sahuayo, Michoac´an, Mexico
of magnetization is cluster size dependent. A thorough cluster-geometry optimizations together with a collinear and noncollinear magnetic moment arrangement sampling including the spin-orbit coupling are carried out to identify the ground-state and the lowlying structures. The relative directions between Co and Pt magnetic moments induced by spin-orbit interaction show an early tendency to arrange the magnetic moments along with Co and Pt layers in a way resembling the L10 phase with tetragonal crystal lattice which can be appreciated in the clusters having N ≥ 5 atoms. Our results show that planar-like structures are preferred in small cluster sizes (N≤ 4 atoms) while for N ≥ 5 tend to form three-dimensional coreshell compact structures with a composition around 50/50% ordering maximizing the number of Co-Pt bonds. The average magnetic moment per atom μ¯ T increases approximately linearly with Co content and important enhancement of the local Co moments is observed as a result of Pt doping for n + m ≤ 4. This is mainly a consequence of the increase in the number of Co d holes due to Co to Pt charge transfer. Finally, our results show important spin and orbital moments induced at the Pt atoms as well as significant orbital moments at the Co atoms .
P. Ruiz-D´ıaz () Instituto de F´ısica, Universidad Aut´onoma de San Luis ´ Potos´ı, Alvaro Obreg´on, 78000 San Luis Potos´ı, Mexico e-mail: [email protected]
Keywords CoPt core-shell alloy clusters · Magnetic anisotropy · Ab initio calculations · Binary nanoalloys · Modeling and simulation
Abstract The ground-state magnetic properties of Con Ptm binary alloy clusters of size N = n + m ≤ 9 are studied systematically as a function of size, composition, and chemical order in the framework of the generalized gradient approximation (GGA) to density functional theory (DFT). Interestingly, strong clustersize and chemical-composition dependence exhibiting substantial values (0.4–22 meV/atom) in the magnetic anisotropy energy (MAE) are revealed. Such behavior crucially depends on the Pt moments induced by the proximity to Co, and on the resulting spinorbit interactions at the Pt atoms. Moreover, we show that the MAEs and direction of magnetization can be tuned to some extent by varying the Pt concentration showing spin reorientations and the easy axis
J. L. Ricardo-Ch´avez Facultad de Ciencias F´ısico-Matem´aticas and Laboratorio Nacional de Superc´omputo, Benem´erita Universidad Aut´onoma de Puebla, Calle 4 Sur No. 104, Col. Centro, C. P. 72000, Puebla, Mexico
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Introduction Magnetic nanoalloys ha
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