Magnetic properties of small Pt-capped Fe, Co, and Ni clusters: A density functional theory study

Abstract

Theoretical studies on M 13 (M = Fe, Co, Ni) and M 13 Pt n (for n = 3, 4, 5, 20) clusters including the spin-orbit coupling are done using density functional theory. The magnetic anisotropy energy (MAE) along with the spin and orbital moments are calculated for M 13 icosahedral clusters. The angle-dependent energy differences are modelled using an extended classical Heisenberg model with local anisotropies. From our studies, the MAE for Jahn-Teller distorted Fe 13 , Mackay distorted Fe 13 and nearly undistorted Co 13 clusters are found to be 322, 60 and 5 µeV/atom, respectively, and are large relative to the corresponding bulk values, (which are 1.4 and 1.3 µeV/atom for bcc Fe and fcc Co, respectively.) However, for Ni 13 (which practically does not show relaxation tendencies), the calculated value of MAE is found to be 0.64 µeV/atom, which is approximately four times smaller compared to the bulk fcc Ni (2.7 µeV/atom). In addition, MAE of the capped cluster (Fe 13 Pt 4 ) is enhanced compared to the uncapped Jahn-Teller distorted Fe 13 cluster.

Electronic and magnetic properties of bimetallicL10cuboctahedral clusters by means of fully relativistic density-functional-based calculations

“…We will see that most of all the studied NPs have the same easy axis orientation as their bulk alloys. Also, the values of the total MAE obtained in this work are of order of tens of meV following the same trend shown by other groups for small NPs [31,32]. In the graphs, the MAE is expressed in meV per atom by dividing by the total number of atoms (magnetic plus non-magnetic) of each NP and using straight coloured lines we show the MAE values for each L1 0 alloy.…”

“…These clusters or nanoparticles (NPs) have properties different from those of bulk alloys due to their reduced surface atomic coordination. In particular, binary 3d-5d NPs formed by transition metals (TM) such as Fe or Co together with 5d noble metals like Au or Pt allow the possibility to tune the magnetic properties based on an in-depth knowledge of their geometrical [27][28][29] and magnetic behavior [30][31][32].…”

“…These results opened a route to understand and fabricate high density magnetic recording materials using deposited NPs on surfaces. There are several experimental [38,39] and theoretical [28][29][30][31][32][40][41][42][43][44][45] studies regarding isolated NPs aiming to obtain the best morphologies and magnetic behavior covering monometallic NPs [29][30][31], binary alloys [28,42,43,45] and even capped NPs [32,44]. Gruner et al have carried out a total energy study of a wide range of structures of various shapes and sizes for (Fe,Co)Pt NPs [28] as well as for Fe(Pd,Ni) [45].It was found that the most energetically favored structures obtained were those of ordered multiply twinned icosahedra and decahedra shapes.…”

Correlation effects and orbital magnetism of Co clusters

“…[10], it is shown that the calculated spin moment in general is in reasonable agreement with experiment. Although the calculated spin and orbital magnetic moments of Co 13 clusters capped with Pt [22] are available, there are no experimental data to compare with these calculations. The latter are also performed within GGA, which is in the present work shown to be inadequate for these systems, e.g., by severely underestimating the orbital magnetic moments with respect to experiment [9,10].…”

Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: Tight-binding and first-principles studies

“…The magnetic anisotropy energy of magnetic nanocrystals (e.g., Fe, Co, Ni, etc.) is the subject of intense experimental [2][3][4][5] and theoretical [6][7][8][9][10][11] studies but the ability to grow well-defined magnetic crystalline nanostructures is also a major issue [12][13][14][15][16][17][18]. This is especially the case for Fe and Co nanoclusters that can adopt various crystalline bulk structures, in particular the body-centered-cubic (bcc) and the face-centered-cubic (fcc) structures in low dimensions [15,16].…”