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

Abstract

We report tight-binding and density functional theory calculations of magnetocrystalline anisotropy energy (MAE) of free Fe (body-centered-cubic) and Co (face-centered-cubic) slabs and nanocrystals. The nanocrystals are truncated square pyramids which can be grown experimentally by deposition of metal on a SrTiO 3 (001) substrate. For both elements our local analysis shows that the total MAE of the nanocrystals is largely dominated by the contribution of (001) facets. However, while the easy axis of Fe (001) is out-of-plane, it is in-plane for Co(001). This has direct consequences on the magnetic reversal mechanism of the nanocrystals. Indeed, the very high uniaxial anisotropy of Fe nanocrystals makes them a much better potential candidate for magnetic storage devices.

Magnetocrystalline anisotropy of Fe and Co slabs and clusters onSrTiO3by first-principles

“…[16]. The Fe(Co)|SrTiO 3 interface was simulated by 10 layers of bcc-Fe(001)[fcc-Co(001)] slab deposited on a SrTiO 3 (001) terminated by TiO 2 with five layers.…”

“…Generalized gradient approximation in Perdew, Burke, and Ernzerhof parametrization [19] was used for electronic exchange-correlation functionals and a plane wave basis set with the cutoffs of 30 Ry and 300 Ry were employed for the wave functions and for the charge density, respectively. The MCA was calculated from the band energy difference between two magnetic orientationm 1 and m 2 using force theorem [16], as we implemented recently in QE package:…”

“…Enhancing MCA of nanostructures provides a route towards future miniaturization of data storage at ultimate length scales [13,14] In our previous work, we demonstrated that for both truncated-pyramid shaped Fe and Co nanocrystals, the MCA of free nanocrystals is mainly dominated by the basal (001) facets resulting in an opposite behavior: out-of-plane and in-plane magnetization direction favored in Fe and Co nanocrystals, respectively [15,16]. Therefore, the study of magnetic properties of nanocrystals deposited on a SrTiO 3 as experimentally obtainable [16,17], is essential, since a considerable influence on the overall behavior of the nanocrystals is expected due to * alexander.smogunov@cea.fr the bonding between the substrate and basal (001) facet. In this paper, we report first-principles investigations of the MCA of bcc-Fe(001) and fcc-Co(001) deposited on a SrTiO 3 substrate, namely Fe(Co)|SrTiO 3 interface.…”

Efficient technique for ab-initio calculation of magnetocrystalline anisotropy energy

“…However, the cumbersome diagonalizations are rather time-consuming, especially when SOC is included, and reaching the energy minimal becomes much harder in the SCF iterations. According to the FT [7,20,1,30,31,32], the main contribution to the MCAE originates from the difference of band energies between two magnetization directions at fixed potential,…”

Perpendicular magnetocrystalline anisotropy energy (MAE) of 111-surface slab of Fe2CoAl

“…In most cases, the half-metallicity and other physical properties are destroyed when cleaveged to low dimension surface slab and 2D thin film from the bulk materials. The nano-scale object loses its magnetic stability with the lowering of size scaled [5]. The stabilization of surface magnetization and magnetic crystalline anisotropy of the magnetic materials at its nano-scale, thin film and surface level for successful device application is an outmost challenge.…”