Estimation of sp–d exchange constants revisited

Abstract

We present a new computational method for estimating the sp–d exchange constant, J eff s p − d , applicable to transition metal doped diluted magnetic semiconductors, transition metal oxides, and 2D- and 3D- dichalcogenides. The proposed method is based on results describing the variation of the magnetic features of a doped system with the variation of its magnetization density (M). The results for J eff s p − d ( M ) obtained with the proposed method are compared with the corresponding results, J eff s p − d ( Δ E VBM ) , obtained from estimations of the spin electron orbital splitting, ΔE VBM, at the valence band maximum (VBM). The latter is estimated in two ways; either directly from plots of the band structure calculations or by calculating the energy difference between the band-centers of the spin-up and spin-down electron density of states of the doped systems. Despite the inherent drawbacks in these two estimation methods for ΔE VBM, they lead to equivalent results and the corresponding J eff s p − d ( Δ E VBM ) are in good agreement with the J eff s p − d ( M ) ones. Ab initio results obtained for the 2D-MoS2 doped with 3d-series transition metals are presented to demonstrate the validity and applicability of the proposed computational schemes for obtaining J eff s p − d . The proposed methods can be utilized as useful tools in the search of new materials for spintronics and valleytronics applications.

Crystal Growth and Physical Properties Evolution in Co‐Doped NiTe2 System

“…Similar magnetic behaviors were also found in some dilute magnetic semiconductor materials. [ 36 ] Sarkar et al reported room temperature antiferromagnetic of Nd 1.90 Co 0.10 O 3− δ nanocrystalline and confirmed that the antiferromagnetic to ferromagnetic phase transition occurs at about 100 K. [ 28 ] Fe x Cr 2− x O 3 nanoparticles were reported to have the same magnetic transition and confirmed that oxygen defects are a key factor to induce magnetic behavior by the bound magnetic polaritons (BMP) model. [ 37 ] In Figure 4, the BMP model is applied to further analyze the origin of the magnetic transition.…”

Magnetism versus band-gap relationship in diluted magnetic semiconductors: megatom impurity behavior of the magnetic dopant complexes

“…Correspondingly, the right panel of figure 4 shows the dependence of E (n,σ) H on the band gap value, e (n,σ) gap . Similar plots have also been found for the systems Ga(TM n )N, TM = Ti, V, Cr, Fe, Ni. In view of our previous reports (see, for example, reference [20] and references therein), the left panel of figure 4 describes the local aspect of the doping process. On the other hand, the right panel of figure 4 describes the holistic view of the doping.…”

“…In equation ( 9), C( f d , f an ) is a factor depending on the band fillings of megatom and host anions; e dX is the d-band center of the d-bands of the dopant formation of the megatom; e p,an is the p-band center of the p-bands of the anions of the system and V dX,sp is the coupling between the cations of the megatom and the host anions. The latter can be approximated by the sp-d magnetic coupling, J sp-d , between the d-band of the megatom and the host anions [24]. Variations, δM tot (correspondingly, variations δe gap ), will affect the megatom's orbital energies e dX (expressed, for example, within a Hubbard-U term, ≈ U M ).…”

“…However, the inverse dependence on |e dX − e p,an | appears to be applicable separately for the early and separately for the late 3D-TM dopant complexes. This can be attributed to the large electronegativity mismatch between the host and dopant cations incorporated as a scaling factor within the constant C( f d , f an ) of equations ( 9) and (10) (see also reference [20] and references therein).…”

Codoping induced enhanced ferromagnetism in diluted magnetic semiconductors

“…Recently, we proposed a new computational method for specifying the GK-product [104,117,118]. It is based on the response properties of the doped system in the imposed boundary condition on magnetization density, M, of the system.…”