Reliability and applicability of magnetic-force linear response theory: Numerical parameters, predictability, and orbital resolution

Abstract

We investigated the reliability and applicability of so-called magnetic force linear response method to calculate spin-spin interaction strengths from first-principles. We examined the dependence on the numerical parameters including the number of basis orbitals and their cutoff radii within nonorthogonal LCPAO (linear combination of pseudo-atomic orbitals) formalism. It is shown that the parameter dependence and the ambiguity caused by these choices are small enough in comparison to the other computation approach and experiments. Further, we tried to pursue the possible extension of this technique to a wider range of applications. We showed that magnetic force theorem can provide the reasonable estimation especially for the case of strongly localized moments even when the ground state configuration is unknown or the total energy value is not accessible. The formalism is extended to carry the orbital resolution from which the matrix form of the magnetic coupling constant is calculated. From the applications to Fe-based superconductors including LaFeAsO, NaFeAs, BaFe2As2 and FeTe, the distinctive characteristics of orbital-resolved interactions are clearly noticed in between single-stripe pnictides and double-stripe chalcogenides.arXiv:1710.07533v1 [cond-mat.str-el]

Calculating temperature-dependent properties of Nd2Fe14B permanent magnets by atomistic spin model simulations

“…The exchange parameters J Fe-Fe ij and J Fe-Nd ij in Eq. 1 are evaluated in the relaxed unit cell (lattice parameters are kept constant as a = b = 8.76Å, c = 12.13Å and the thermal expansion is not considered) by using OpenMX [37][38][39][40]. The calculation of Heisenberg exchange parameters J ij between two different atomic sites i and j is implemented in OpenMX by using the magnetic-force theorem (follow the original formalism by Liechtenstein et al [37]) and its extension to the nonorthogonal LCPAO (linear combination of pseudoatomic orbitals) method [38].…”

“…The calculation of Heisenberg exchange parameters J ij between two different atomic sites i and j is implemented in OpenMX by using the magnetic-force theorem (follow the original formalism by Liechtenstein et al [37]) and its extension to the nonorthogonal LCPAO (linear combination of pseudoatomic orbitals) method [38]. In detail, J ij is estimated as a response to small spin tiltings (as a perturbation) from the given converged solution, as shown the detailed formulation in [37][38][39]. More application examples of OpenMX in calculating Heisenberg exchange parameters are reported by the OpenMX's developers in the literature [38][39][40][41].…”

“…In detail, J ij is estimated as a response to small spin tiltings (as a perturbation) from the given converged solution, as shown the detailed formulation in [37][38][39]. More application examples of OpenMX in calculating Heisenberg exchange parameters are reported by the OpenMX's developers in the literature [38][39][40][41]. In fact, the unit cell here is already very large and thus the lattice translation vectors have negligible influence on the calculated J ij .…”

Induced magnetic two-dimensionality by hole doping in the superconducting infinite-layer nickelate Nd1−xSrxNiO2

“…We performed MFT (magnetic force theory) calculations [32,33] to obtain magnetic exchange couplings on top of DFT electronic structures obtained from OpenMX software package [26,27]. The calculations were carried out using our recently-developed MFT code [34,35]. We adopted the most stable G-type AFM order as the input for our MFT calculations.…”

Calculating magnetic interactions in organic electrides

“…In order to meet this challenge, here we introduce a new approach. First we employ so-called 'magnetic force response theory (MFT)' [24][25][26][27][28][29] for calculating magnetic interactions.…”