<i>Ab initio</i>
 dynamical exchange interactions in frustrated antiferromagnets

Simoni, Jacopo; Stamenova, Maria; Sanvito, Stefano

doi:10.1103/physrevb.96.054411

Cited by 10 publications

(10 citation statements)

References 35 publications

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“…As such one expects ∆ (and hence the torque) to change sign as the local magnetisation changes sign (as in the case of antiferromagnets). Furthermore one can show that |∆| ∼ Im, where I is the Stoner parameter [20]. This means that for similar Stoner coupling the exchange and correlation field is more intense for materials presenting larger magnetization.…”

Section: Discussionmentioning

confidence: 91%

Nontrivial spatial dependence of the spin torques in L10 FePt-based tunneling junctions

2019

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We present an ab-initio study of the spin-transfer torque in a Fe/MgO/FePt/Fe magnetic tunnel junctions. We consider a FePt film with a thickness up to six unit cells, either in direct contact with the MgO spacer or with an intercalated ultra-thin Fe seed layer. We find that in the FePt layer the torque is not attenuated as strongly as in the case of pure Fe. Moreover, in FePt the torque alternates sign at the Fe and Pt atomic planes throughout the stack for all FePt thicknesses considered. Finally, when Fe is intercalated between MgO and L10-FePt, the torque is sharply attenuated and it is transferred to FePt only for a Fe seed layer that is less than two-atomic-planes thick. We attribute these features to the different spatial profiles of the exchange and correlation field and the induced non-equilibrium spin accumulation. The calculated tunnelling magneto-resistance of the Fe/MgO/FePt/Fe junctions studied is enhanced with respect to the one of Fe/MgO/Fe, while it is reduced with Fe intercalation. Our work shows that L10-FePt junctions can be promising candidates for current-operated magnetic devices and that the magnetic texture at the atomic scale has an important effect on the spin transfer torque. arXiv:1810.04136v1 [cond-mat.mtrl-sci]

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Section: Discussionmentioning

confidence: 91%

Nontrivial spatial dependence of the spin torques in L10 FePt-based tunneling junctions

2019

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“…The effects of electron-electron interactions come into this noninteracting KS system via an effective potential, the so called Hartree exchange-correlation (XC) potential. Although TDDFT is an exact theory for treating systems under the influence of strong time-dependent external potentials [10][11][12][13][14][15][16][17] , it is most commonly applied within the weak perturbation limit. When working in this linear regime, one requires the functional derivative of the XC potential, the so called XC kernel.…”

Section: Introductionmentioning

confidence: 99%

Adiabatic generalized gradient approximation kernel in time-dependent density functional theory

et al. 2019

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A complete understanding of a material requires both knowledge of the excited states as well as of the ground state. In particular, the low energy excitations are of utmost importance while studying the electronic, magnetic, dynamical, and thermodynamical properties of the material. Time-Dependent Density Functional Theory (TDDFT), within the linear regime, is a successful ab-initio method to access the electronic charge and spin excitations. However, it requires an approximation to the exchange-correlation (XC) kernel which encapsulates the effect of electron-electron interactions in the many-body system. In this work we derive and implement the spin-polarized XC kernel for semi-local approximations such as the adiabatic Generalized Gradient Approximation (AGGA). This kernel has a quadratic dependence on the wavevector, q, of the perturbation, however the impact of this on the electron energy loss spectra (EELS) is small. Although the GGA functional is good in predicting structural properties, it generality overestimates the exchange spin-splitting. This leads to higher magnon energies, as compared to both ALDA and experiment. In addition, interaction with the Stoner spin-flip continuum is enhanced by AGGA, which strongly suppresses the intensity of spin-waves. arXiv:1808.00215v1 [cond-mat.mtrl-sci] 1 Aug 2018

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“…( 1) in time one needs to approximate v xc and B xc . Usually adiabatic extensions of ground-state functionals like LSDA are used in such timepropagation scheme [36][37][38][39][40]. LSDA is a collinear functional by design and requires only ρ ↑ and ρ ↓ as input.…”

Section: B Functionalmentioning

confidence: 99%

Effect of exchange-correlation spin–torque on spin dynamics

2018

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A recently proposed exchange-correlation functional with in density functional theory, which ensures that the exchange-correlation magnetic field is source-free, is shown to give non-zero internal spin-torque. This spin-torque is identically zero for all conventional local and semi-local functionals. Extension of this source-free functional to the time domain is used to study the effect of the internal spin-torque on the laser induced spin-dynamics in bulk Co, Ni and interfaces of these metals with Pt. It is shown that the internal spin-torque contribute significantly to spin-dynamics only when the magneto crystalline anisotropy energy is small, as in the case of cubic bulk materials. For surfaces or interfaces, where the anisotropy energy is large, these torques are too small to cause any significant precession of spins in early times (< 100fs). Further more it is shown that the spin-dynamics caused by the internal spin-torque is slow compared to the inter-site spin transfer and spin-orbit mediated spin-flips.

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Ab initio dynamical exchange interactions in frustrated antiferromagnets

Cited by 10 publications

References 35 publications

Nontrivial spatial dependence of the spin torques in L10 FePt-based tunneling junctions

Nontrivial spatial dependence of the spin torques in L10 FePt-based tunneling junctions

Adiabatic generalized gradient approximation kernel in time-dependent density functional theory

Effect of exchange-correlation spin–torque on spin dynamics

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