GaMnAs on InGaAs templates: Influence of strain on the electronic and magnetic properties

Daeubler, J.; Schwaiger, Stephan; Glunk, M.; Tabor, M.; Schoch, W.; Sauer, R.; Limmer, W.

doi:10.1016/j.physe.2007.08.049

Cited by 16 publications

(16 citation statements)

References 8 publications

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“…21,22 Part of the experimental data has already been published in conference proceedings. 23 Here, we combine the earlier with the present extensive experimental findings advancing a quantitative comparison of the intrinsic anisotropy parameters with model calculations for the MA, performed within the meanfield Zener model introduced by Dietl et al 5 Note that several samples analyzed in Ref. 23 have been substituted by new samples grown under optimized conditions and that the sample series has been expanded by one specimen with zz = −0.38%.…”

Section: Introductionmentioning

confidence: 95%

Magnetic anisotropy in (Ga,Mn)As: Influence of epitaxial strain and hole concentration

et al. 2009

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We present a systematic study on the influence of epitaxial strain and hole concentration on the magnetic anisotropy in ͑Ga,Mn͒As at 4.2 K. The strain was gradually varied over a wide range from tensile to compressive by growing a series of ͑Ga,Mn͒As layers with 5% Mn on relaxed graded ͑In,Ga͒As/GaAs templates with different In concentration. The hole density, the Curie temperature, and the relaxed lattice constant of the as-grown and annealed ͑Ga,Mn͒As layers turned out to be essentially unaffected by the strain. Angledependent magnetotransport measurements performed at different magnetic-field strengths were used to probe the magnetic anisotropy. The measurements reveal a pronounced linear dependence of the uniaxial out-of-plane anisotropy on both strain and hole density. Whereas the uniaxial and cubic in-plane anisotropies are nearly constant, the cubic out-of-plane anisotropy changes sign when the magnetic easy axis flips from in-plane to out-of-plane. The experimental results for the magnetic anisotropy are quantitatively compared with calculations of the free energy based on a mean-field Zener model. Almost perfect agreement between experiment and theory is found for the uniaxial out-of-plane and cubic in-plane anisotropy parameters of the as-grown samples. In addition, magnetostriction constants are derived from the anisotropy data.

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Section: Introductionmentioning

confidence: 95%

Magnetic anisotropy in (Ga,Mn)As: Influence of epitaxial strain and hole concentration

et al. 2009

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“…Indeed, novel functionalities or physical effects have already been demonstrated in spin-electronic devices based on GaMnAs, such as the emission of circularly polarized light from a socalled spin light emitting diode, 12,16 the controlled motion of domain walls via current pulses, 17,18 the tunneling anisotropic magnetoresistance in GaMnAs/insulator/normal metal structures, 19 and nonvolatile memory device concepts. 4,7,8 One of the most intriguing properties of DMS is the strong dependence of their magnetic properties on nonmagnetic parameters, such as electric field, 20,21 light irradiation, [22][23][24] temperature, [25][26][27] dopant density, 28,29 strain, [30][31][32][33] or pressure. 34 This allows for various control schemes of the magnetic properties of DMS, which we shortly discuss in the following.…”

Section: Introductionmentioning

confidence: 99%

“…Also the magnetic anisotropy in GaMnAs was found to qualitatively change as a function of strain. [30][31][32][33] Ga 1−x Mn x As layers grown on GaAs are compressively strained, leading to a first-order uniaxial magnetic anisotropy so that the film plane is an easy magnetic plane for the typical range of Mn concentrations ͑0.01Ͻ x Ͻ 0.1͒. [30][31][32] A smaller cubic ͑biaxial͒ anisotropy yields two approximately orthogonal easy axes within the film plane.…”

Section: Introductionmentioning

confidence: 99%

Ga1−xMnxAs/piezoelectric actuator hybrids: A model system for magnetoelastic magnetization manipulation

et al. 2008

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We have investigated the magnetic properties of a piezoelectric actuator/ferromagnetic semiconductor hybrid structure. Using a GaMnAs epilayer as the ferromagnetic semiconductor and applying the piezo stress along its ͓110͔ direction, we quantify the magnetic anisotropy as a function of the voltage V p applied to the piezoelectric actuator using anisotropic magnetoresistance techniques. As the magnetic anisotropy in GaMnAs substantially changes as a function of temperature T, the ratio of the magnetoelastic and the magnetocrystalline anistropies can be tuned from approximately 1/4 to 4. Thus, GaMnAs/piezoelectric actuator hybrids are an ideal model system for the investigation of different piezoelastic magnetization control regimes. At T = 5 K the magnetoelastic term is a minor contribution to the magnetic anisotropy. Nevertheless, we show that the switching fields of ͑ 0 H͒ loops are shifted as a function of V p at this temperature. At 50 K-where the magnetoelastic term dominates the magnetic anisotropy-we are able to tune the magnetization orientation by about 70°solely by means of the electrical voltage V p applied. Furthermore, we derive the magnetostrictive constant 111 as a function of temperature and find values consistent with earlier results. We argue that the piezo voltage control of magnetization orientation is directly transferable to other ferromagnetic/piezoelectric hybrid structures, paving the way to innovative multifunctional device concepts. As an example, we demonstrate piezo voltageinduced irreversible magnetization switching at T = 40 K, which constitutes the basic principle of a nonvolatile memory element.

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“…Magnetic torque calculations simulating the strain-induced effects in the alloy with 5% Mn yield a linear variation of the magnetic anisotropy energy E [100] − E [001] from +3.38 to −3.37 μeV per unit cell for a c/a ratio varying from 0.99 to 1.01, i.e., the magnetic easy axis changes from an out-of-plane to an in-plane orientation, which is in line with corresponding experimental data. [31][32][33] The magnetic dipole-dipole interactions lead in film geometry to the in-plane (uniform within the plane) anisotropy with the energy E dip ≈ 0.24 μeV per unit cell in the case of an alloy with 5% Mn and Mn magnetic moments 3.7μ B /atom. This is smaller by an order of magnitude than the strain-induced MCA.…”

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confidence: 99%

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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GaMnAs on InGaAs templates: Influence of strain on the electronic and magnetic properties

Cited by 16 publications

References 8 publications

Magnetic anisotropy in (Ga,Mn)As: Influence of epitaxial strain and hole concentration

Magnetic anisotropy in (Ga,Mn)As: Influence of epitaxial strain and hole concentration

Ga1−xMnxAs/piezoelectric actuator hybrids: A model system for magnetoelastic magnetization manipulation

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

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