Mechanism of Uniaxial Magnetocrystalline Anisotropy in Transition Metal Alloys

Kota, Yohei; Sakuma, Atsushi

doi:10.7566/jpsj.83.034715

Cited by 67 publications

(45 citation statements)

References 55 publications

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“…(1). Here, m = t Py /t Pt is thickness ratio of Py and Pt layer; ζ = λ Pt /λ Py = 7.46, which is strength ratio of spin orbit coupling of Pt (λ Pt ) and Py (λ Py ), taking the literature valve λ Pt = 554 meV 21 and λ Py = 74.28 meV based on the tight-binding sense; 21,22 η = N Pt /N P y =1.02 is conduction-electron-density ratio of Pt (N Pt ) and Py (N P y ), where the number of valence electron are adopted for the values approximately. P is spin polarization of Py, which is 0.3 ∼ 0.5 usually, and here P is taken as an intermediate value 0.4.…”

Section: Resultsmentioning

confidence: 99%

Origin of enhanced anomalous Hall effect in ultrathin Pt/permalloy bilayers

Zhang

Sun

et al. 2016

AIP Advances

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There are two mechanisms which could enhance spin-dependent scattering in a low dimensional Pt/Ferromagnetic metal structure. One is magnetic proximity effect. The other is spin orbit coupling proximity effect which was suggested recently. This work demonstrates that, through a series of experiments on anomalous Hall effect, the spin orbit coupling proximity effect dominates the enhancement in very thin Pt/Permalloy bilayers. It may help to find a way to optimize magnetic transport property of spintronics devices in which the spin orbit coupling is deeply involved.

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Section: Resultsmentioning

confidence: 99%

Origin of enhanced anomalous Hall effect in ultrathin Pt/permalloy bilayers

Zhang

Sun

et al. 2016

AIP Advances

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“…Considering the strong dependence of the MAE on the electron band structure details discussed in the previous section and the fact that the agreement with FT is not homogeneous as N e changes, both facts suggest that 2PT loses its validity for elements with strong SOI. Thus, the coincidence in the neutral-case FePt and FeAu MAEs could be considered to be fortuitous, in the sense that the coincidence is a consequence of the specific band structure of the alloy, as it is the case of FePt (also observed in [62]) and FeAu 5 . 5 In the FeAu alloy, the Au-d states are mostly confined in a band between −7 and −4 eV below the Fermi energy (see figure 2).…”

Section: Non-neutral Systemsmentioning

confidence: 98%

Validity of perturbative methods to treat the spin–orbit interaction: application to magnetocrystalline anisotropy

2019

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A second-order perturbation (2PT) approach to the spin-orbit interaction (SOI) is implemented within a density-functional theory framework. Its performance is examined by applying it to the calculation of the magnetocrystalline anisotropy energies (MAE) of benchmark systems, and its efficiency and accuracy are compared with the popular force theorem method. The case studies are tetragonal FeMe alloys (Me=Co, Cu, Pd, Pt, Au), as well as FeMe (Me=Co, Pt) bilayers with (111) and (100) symmetry, which cover a wide range of SOI strength and electronic band structures. The 2PT approach is found to provide a very accurate description for 3d and 4d metals and, moreover, this methodology is robust enough to predict easy axis switching under doping conditions. In all cases, the details of the bandstructure, including states far from the Fermi level, are responsible for the finally observed MAE value, sometimes overruling the effect of the SOI strength. From a technical point of view, it is confirmed that accuracy in the MAE calculations is subject to the accuracy of the Fermi level determination.The interplay of MCA and dimensionality is considered as a promising route for the development of spintronics. Furthermore, MCA plays a central role in the magnetic properties of two-dimensional materials, since it can prevent thermal fluctuations from destroying long-range magnetic order [8]. In this context, density functional theory (DFT) calculations that include SOI constitute a powerful theoretical tool to characterize the MCA. Nonetheless, the small magnitude of the associated magnetocrystalline anisotropy energy (MAE) imposes stringent convergence to the DFT calculations at the expense of high computational demands. In practice, fully relativistic DFT calculations that include SOI are carried out by first computing self-consistently the Hamiltonian of the system including the scalar relativistic term and next adding the spin-orbit contribution. The latter may be treated self-consistently (FSC) or non-self-consistently [9, 10] within the so-called force theorem (FT) [11] to obtain the MAE. FT is often considered to produce a good estimate of the FSC MAE value for every system, at least for bulk crystals, although it has been shown to be less accurate in the case of low dimensional systems [12]. In any case, this comparison between FT and SCF calculations can only be done for relatively simple systems, because the FSC tends to be computationally too demanding. Alternatively, Green's function methods that treat SOI at the level of second-order perturbation theory (2PT) have been formulated in the literature under different flavours [13][14][15][16][17]. These approaches rely on the knowledge of the spin-orbit effects on atomic orbitals (AOs) [18][19][20], which can be quasi-analytically accounted. However, to our knowledge, the versatility of those perturbative methods has not been exploited within a DFT environment. Considering the high computational expense involved in DFT calculations that include SOI under the aforemention...

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“…C. Crystal structure of L10 compounds We chose to focus on L1 0 magnetic compounds because they are one of the most widely studied systems [27][28][29]. Their simple CuAu-type crystal structure is shown in Fig.…”

Section: Scaling Soc Strengthmentioning

confidence: 99%

Intersublattice magnetocrystalline anisotropy using a realistic tight-binding method based on maximally localized Wannier functions

2019

Phys. Rev. B

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Using a realistic tight-binding Hamiltonian based on maximally localized Wannier functions, we investigate the two-ion magnetocrystalline anisotropy energy (MAE) in L10 transition metal compounds. MAE contributions from throughout the Brillouin zone are obtained using magnetic force theorem calculations with and without perturbation theory. The results from both methods agree with each other, and both reflect features of the Fermi surface. The intrasublattice and intersublattice contributions to MAE are evaluated using a Greens function method. We find that the sign of the intersublattice contribution varies among compounds, and that its amplitude may be significant, suggesting MAE can not be resolved accurately in a single-ion manner. The results are further validated by scaling spin-orbit-coupling strength in density functional theory. Overall, this realistic tight-binding method provides an effective approach to evaluate and analyze MAE while retaining the accuracy of corresponding first-principles methods.

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Mechanism of Uniaxial Magnetocrystalline Anisotropy in Transition Metal Alloys

Cited by 67 publications

References 55 publications

Origin of enhanced anomalous Hall effect in ultrathin Pt/permalloy bilayers

Origin of enhanced anomalous Hall effect in ultrathin Pt/permalloy bilayers

Validity of perturbative methods to treat the spin–orbit interaction: application to magnetocrystalline anisotropy

Intersublattice magnetocrystalline anisotropy using a realistic tight-binding method based on maximally localized Wannier functions

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