Magnetic interactions in BiFeO3 : A first-principles study

Abstract

First-principles calculations, in combination with the four-state energy mapping method, are performed to extract the magnetic interaction parameters of multiferroic BiFeO3. Such parameters include the symmetric exchange (SE) couplings and the Dzyaloshinskii-Moriya (DM) interactions up to second nearest neighbors, as well as the single ion anisotropy (SIA). All magnetic parameters are obtained not only for the R3c structural ground state, but also for the R3m and R3c phases in order to determine the effects of ferroelectricity and antiferrodistortion distortions, respectively, on these magnetic parameters. In particular, two different second-nearest neighbor couplings are identified and their origins are discussed in details. Moreover, Monte-Carlo (MC) simulations using a magnetic Hamiltonian incorporating these first-principles-derived interaction parameters are further performed. They result (i) not only in the accurate prediction of the spin-canted G-type antiferromagnetic structure and of the known magnetic cycloid propagating along a <110> direction, as well as their unusual characteristics (such as a weak magnetization and spin-density-waves, respectively); (ii) but also in the finding of another cycloidal state of low-energy and that awaits to be experimentally confirmed. Turning on and off the different magnetic interaction parameters in the MC simulations also reveal the precise role of each of them on magnetism.

Topological spin texture in Janus monolayers of the chromium trihalides Cr(I, X)3

“…Let us now look at the precise values of the magnetic parameters obtained from DFT and four-state method 13,[19][20][21] . As shown in Table I Another important factor that affects the formation of skyrmions is the magnetic anisotropy energy (MAE), which is defined as the energy difference between out-of-plane FM (zFM) and inplane FM (xFM) states, = E zF M − E xF M , where < 0 (> 0, respectively) favors out-of-plane (in-plane, respectively) FM.…”

Ab initio methodology for magnetic exchange parameters: Generic four-state energy mapping onto a Heisenberg spin Hamiltonian

“…[15,16] also presented the technique to calculate DMI parameters in detail. As a consequence of the recent advance in field of 2D magnetism, the impact of studies involving magnetic chirality is growing rapidly [5,20,21]. However, in both Refs.…”

A magnetic phase diagram for nanoscale epitaxial BiFeO3 films

“…Since in (110)-oriented BFO the type-2 cycloid is almost exclusively observed, 18,39 our calculations consider this cycloid along with various collinear antiferromagnetic arrangements with different spin directions. The effective Hamiltonian approach considers nearest and next-nearest neighbors 48 in the spincurrent model, [49][50][51][52] and in the present calculations the spin-current parameters C 1 and C 2 were chosen to reproduce the d dependence of the magnetic ground state at 0.7% strain. In the simulations, the value of strain (taken from the experiment for the typical strain values when BFO is grown on STO substrate) was fixed at e ¼ þ0.7%, and the distortion d was systematically swept between 0% and 1.5%.…”