Atomistic spin dynamics of low-dimensional magnets

Abstract

We investigate the magnetic properties of a range of low-dimensional ferromagnets using a combination of first-principles calculations and atomistic spin dynamics simulations. This approach allows us to evaluate the ground state and finite temperature properties of experimentally well characterized systems such as Co/Cu(111), Co/Cu(001), Fe/Cu(001) and Fe/W(110), for different thicknesses of the magnetic layer. We compare our calculated spin wave spectra with experimental data available in the literature, and find a good quantitative agreement. We also predict magnon spectra for systems for which no experimental data exist at the moment, and estimate the role of temperature effects.

Magnetic phase diagram of an Fe monolayer on W(110) and Ta(110) surfaces based onab initiocalculations

“…Although the appearance of the spin spiral state as a consequence of the Dzyaloshinsky-Moriya interaction is a well-known effect in two-dimensional systems such as an Mn monolayer [9] or Fe double layer [12] on W(110), there was no such transition observed as a function of temperature. However, ab initio calculations [18][19][20] indicated a ferromagnetic ground state for the Fe double layer on W(110), suggesting that this system is probably very close to such a ferromagnetic-spin spiral transition. We have also shown that the high-wave-vector SS II state may turn into the low-wave-vector SS I spiral by increasing the temperature, while in the case of the SS III-SS II transition the normal vector of the spin spiral rotated from a general in-plane direction towards the [001] direction.…”

“…Using the experimentally obtained wavelength of the low-temperature spiral state it was possible to find micromagnetic exchange (spin stiffness), Dzyaloshinsky-Moriya, and anisotropy parameters describing * rozsa@phy.bme.hu this type of order [12,17]. However, both micromagnetic [18,19] and atomistic [20] ab initio calculations indicated a ferromagnetic ground state in the system. For an Fe monolayer on W(110), theoretical calculations [21][22][23] agree with experiments [24] in determining an in-plane ferromagnetic ground state.…”

Realistic finite temperature simulations of magnetic systems using quantum statistics

“…A common method to simulate finite temperature magnetic properties is to employ a two-step process where in the first step all material specific parameters are calculated within zero-temperature electronic structure theory to construct a simplified statistical physics model which is then solved in the second step by employing atomistic simulations. This methodology has been very successful of qualitatively predicting Curie temperatures and magnon spectra of transition metals, alloys and diluted magnetic semiconductors [4][5][6][7][8][9][10][11][12][13][14] . An overwhelming majority of the reported simulations of this kind have hitherto been based on classical Boltzmann statistics at finite temperature instead of the proper Bose-Einstein quantum statistics.…”

Atomistic-continuum multiscale modelling of magnetisation dynamics at non-zero temperature

“…Thus, the size of the system does not enter the derivations, and, therefore, (if the mean-field assumption is true) equation (9) should be valid for any system size (i.e. equation (9) does not have any scale limitations). In Section 2.2.1, exactly this case is considered.…”

“…In the atomistic approach, the dynamic behaviour of spin magnetic moments of individual atoms is described by the atomistic Landau-Lifshitz-Gilbert equation [9,19]:…”