Magnetocrystalline anisotropies in (Ga,Mn)As: Systematic theoretical study and comparison with experiment

Zemen, Jan; Kučera, Jaroslav; Olejník, K.; Jungwirth, T.

doi:10.1103/physrevb.80.155203

Cited by 78 publications

(132 citation statements)

References 74 publications

(248 reference statements)

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“…Significant variations can be also found in the experimental magnetic anisotropy constants of (Ga,Mn)As (ref. 29). The disarray of the previously measured micromagnetic parameters reflects partly the lack of careful materials optimization but also the limitations of common magnetic characterization techniques when applied to the thin-film dilute-moment (Ga,Mn)As samples.…”

Section: Resultsmentioning

confidence: 99%

The essential role of carefully optimized synthesis for elucidating intrinsic material properties of (Ga,Mn)As

et al. 2013

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(Ga,Mn)As is at the forefront of spintronics research exploring the synergy of ferromagnetism with the physics and the technology of semiconductors. However, the electronic structure of this model spintronics material has been debated and the systematic and reproducible control of the basic micromagnetic parameters and semiconducting doping trends has not been established. Here we show that seemingly small departures from the individually optimized synthesis protocols yield non-systematic doping trends, extrinsic charge and moment compensation, and inhomogeneities that conceal intrinsic properties of (Ga,Mn)As. On the other hand, we demonstrate reproducible, well controlled and microscopically understood semiconducting doping trends and micromagnetic parameters in our series of carefully optimized epilayers. Hand-in-hand with the optimization of the material synthesis, we have developed experimental capabilities based on the magneto-optical pumpand-probe method that allowed us to simultaneously determine the magnetic anisotropy, Gilbert damping and spin stiffness constants from one consistent set of measured data.

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Section: Resultsmentioning

confidence: 99%

The essential role of carefully optimized synthesis for elucidating intrinsic material properties of (Ga,Mn)As

et al. 2013

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“…This term can be evaluated theoretically using an effective mass Hamiltonian with the six-band k.p Luttinger-Kohn term, a strain tensor, and the p-d exchange interaction of the holes and the Mn spins in the molecular-field approximation 21,40 . The saturation magnetization was set to 6 kA.m −1 (T ≈ 95 K), which corresponds to a |B G | ≈4 meV spin splitting parameter 21 .…”

Section: B Derivation Of the Strain Wave Expressionmentioning

confidence: 99%

“…The saturation magnetization was set to 6 kA.m −1 (T ≈ 95 K), which corresponds to a |B G | ≈4 meV spin splitting parameter 21 . The usual biaxial strain terms ε zz,0 , ε xx,0 were set to zero, and a non-zero term idε xz introduced in the Bir-Pikus strain tensor, where d=-4.8 eV is the shear deformation potential 40 . In this way, B c and A 2xz were the only unknown parameters in the free energy density.…”

Section: B Derivation Of the Strain Wave Expressionmentioning

confidence: 99%

Irreversible magnetization switching using surface acoustic waves

et al. 2013

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An analytical and numerical approach is developped to pinpoint the optimal experimental conditions to irreversibly switch magnetization using surface acoustic waves (SAWs). The layers are magnetized perpendicular to the plane and two switching mechanisms are considered. In precessional switching, a small in-plane field initially tilts the magnetization and the passage of the SAW modifies the magnetic anisotropy parameters through inverse magneto-striction, which triggers precession, and eventually reversal. Using the micromagnetic parameters of a fully characterized layer of the magnetic semiconductor (Ga,Mn)(As,P), we then show that there is a large window of accessible experimental conditions (SAW amplitude/wave-vector, field amplitude/orientation) allowing irreversible switching. As this is a resonant process, the influence of the detuning of the SAW frequency to the magnetic system's eigenfrequency is also explored. Finally, another -non-resonantswitching mechanism is briefly contemplated, and found to be applicable to (Ga,Mn)(As,P): SAWassisted domain nucleation. In this case, a small perpendicular field is applied opposite the initial magnetization and the passage of the SAW lowers the domain nucleation barrier.

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“…So far, however, to the best of our knowledge, there is no consensus in the literature concerning the origin of the in-plane uniaxial anisotropy. Although in some recent theoretical works the origin of the uniaxial in-plane anisotropy is attributed to a trigonal distortion caused by a uniaxial or shear strain within the film plane, 13,18,21 this type of distortion was not observed experimentally. Recently, Werpachowska and Dietl 22 suggested that the anisotropy mechanism in (Ga,Mn)As films originates from Dzyaloshinsky-Moriya interactions, without assuming any in-plane lattice distortion within their model.…”

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Spin-orbit coupling effect in (Ga,Mn)As films: Anisotropic exchange interactions and magnetocrystalline anisotropy

et al. 2011

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The magnetocrystalline anisotropy (MCA) of (Ga,Mn)As films has been studied on the basis of ab initio electronic structure theory by performing magnetic torque calculations. An appreciable contribution to the in-plane uniaxial anisotropy can be attributed to an extended region adjacent to the surface. Calculations of the exchange tensor allow to ascribe a significant part to the MCA to the exchange anisotropy, caused either by a tetragonal distortion of the lattice or by the presence of the surface or interface. Diluted magnetic semiconductors (DMSs) are a class of materials having attractive properties for spintronic applications (e.g., see the review in Ref. 1). Many investigations in this field are focused on the (Ga,Mn)As DMS system with 1%-10% of Mn atoms which have promising features from a physical as well as technological point of view. The crucial role of valence states with respect to various magnetic properties of (Ga,Mn)As was discussed in the literature by many authors (e.g., Refs. 1-5, and 6). First of all, the valence-band holes are responsible for ferromagnetic (FM) order in the system mediating the exchange interaction between well-localized Mn magnetic moments. Spin-orbit coupling of the states at the top of valence band, being close to the Fermi level, leads to a rather strong cubic magnetocrystalline anisotropy (MCA) in bulk (Ga,Mn)As and to an in-plane biaxial MCA in the (Ga,Mn)As film on top of a GaAs substrate. [1][2][3] In the latter case the spin-orbit coupling (SOC) makes the valence states close to E F sensitive to lattice distortions and is in that way responsible for the in-plane MCA due to compressive strains originating from the lattice mismatch between the (Ga,Mn)As film and GaAs substrate. [7][8][9][10][11][12][13][14][15][16][17] As soon as the spin polarization of the valence bands becomes rather small, the MCA in (Ga,Mn)As is discussed in terms of anisotropic exchange interactions of the Mn atoms. 2,3,7 The strength of the MCA depends on the hole concentration introduced by the Mn impurity atoms 2,11,18,19 as well as on the variation of the equilibrium lattice parameter of (Ga,Mn)As, which increases with increasing Mn content and results thus in a larger lattice mismatch with the GaAs substrate.Numerous experimental results evidenced a temperature-induced transition from the biaxial to the uniaxial in-plane anisotropy in (Ga,Mn)As films deposited on GaAs. [11][12][13][14][15][16][17][18] In spite of different experimental conditions, the in-plane uniaxial anisotropy was observed for (Ga,Mn)As films in a thickness range from 25 nm (Ref. 20) to 500 nm, 16 irrelevant with respect to the surface condition. So far, however, to the best of our knowledge, there is no consensus in the literature concerning the origin of the in-plane uniaxial anisotropy. Although in some recent theoretical works the origin of the uniaxial in-plane anisotropy is attributed to a trigonal distortion caused by a uniaxial or shear strain within the film plane, 13,18,21 this type of distortion was not obser...

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Magnetocrystalline anisotropies in (Ga,Mn)As: Systematic theoretical study and comparison with experiment

Cited by 78 publications

References 74 publications

The essential role of carefully optimized synthesis for elucidating intrinsic material properties of (Ga,Mn)As

The essential role of carefully optimized synthesis for elucidating intrinsic material properties of (Ga,Mn)As

Irreversible magnetization switching using surface acoustic waves

Spin-orbit coupling effect in (Ga,Mn)As films: Anisotropic exchange interactions and magnetocrystalline anisotropy

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