T. Jungwirth

Czech Academy of Sciences

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Jairo Sinova

Johannes Gutenberg University Mainz

161

R. P. Campion

University of Nottingham

105

V. Novák

Czech Academy of Sciences, Institute of Physics

100

B. L. Gallagher

University of Nottingham

K. Olejník

Czech Academy of Sciences, Institute of Physics

A. H. MacDonald

The University of Texas at Austin

J. Wunderlich

Czech Academy of Sciences, Institute of Physics

LŠ

Libor Šmejkal

Czech Academy of Sciences

K. W. Edmonds

University of Nottingham

P. Wadley

University of Nottingham

Cooperative Institutions

Czech Academy of Sciences, Institute of Physics

125

Czech Academy of Sciences

Centre National de la Recherche Scientifique

Charles University

University of Nottingham

University of Cambridge

Johannes Gutenberg University Mainz

Hitachi (United Kingdom)

Leibniz Institute for Solid State and Materials Research

Tohoku University

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Hole–hole correlation effects on magnetic properties of Mn III1−V diluted magnetic semiconductors

Physica E Low-dimensional Systems and Nanostructures (2001)

T. Jungwirth Byounghak Lee A. H. MacDonald

Magnetic semiconductor

10.1016/s1386-9477(01)00072-8

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Citations (16)

Theory of magnetic anisotropy inIII1−xMnxVferromagnets

Physical review. B, Condensed matter (2001)

Ramin Abolfath T. Jungwirth José M. Brum A. H. MacDonald

We present a theory of magnetic anisotropy in ${\rm III}_{1-x}{\rm Mn}_{x}{\rm V}$ diluted magnetic semiconductors with carrier-induced ferromagnetism. The theory is based on four and six band envelope functions models for the valence band holes and a mean-field treatment of their exchange interactions with ${\rm Mn}^{++}$ ions. We find that easy-axis reorientations can occur as a function of temperature, carrier density $p$, and strain. The magnetic anisotropy in strain-free samples is predicted to have a $p^{5/3}$ hole-density dependence at small $p$, a $p^{-1}$ dependence at large $p$, and remarkably large values at intermediate densities. An explicit expression, valid at small $p$, is given for the uniaxial contribution to the magnetic anisotropy due to unrelaxed epitaxial growth lattice-matching strains. Results of our numerical simulations are in agreement with magnetic anisotropy measurements on samples with both compressive and tensile strains. We predict that decreasing the hole density in current samples will lower the ferromagnetic transition temperature, but will increase the magnetic anisotropy energy and the coercivity.

Magnetic semiconductor

10.1103/physrevb.63.054418

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Citations (321)

Curie Point Singularity in the Temperature Derivative of Resistivity in (Ga,Mn)As

Physical Review Letters (2008)

V. Novák K. Olejník J. Wunderlich M. Cukr Karel Výborný

We observe a singularity in the temperature derivative drho/dT of resistivity at the Curie point of high-quality (Ga,Mn)As ferromagnetic semiconductors with Tc's ranging from approximately 80 to 185 K. The character of the anomaly is sharply distinct from the critical contribution to transport in conventional dense-moment magnetic semiconductors and is reminiscent of the drho/dT singularity in transition metal ferromagnets. Within the critical region accessible in our experiments, the temperature dependence on the ferromagnetic side can be explained by dominant scattering from uncorrelated spin fluctuations. The singular behavior of drho/dT on the paramagnetic side points to the important role of short-range correlated spin fluctuations.

10.1103/physrevlett.101.077201

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Citations (141)

Room-temperature antiferromagnetic memory resistor

Nature Materials (2014)

X. Martí Ignasi Fina Carlos Frontera Jian Liu P. Wadley

Bistability

Magnetic storage

10.1038/nmat3861

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Citations (622)

Theory of ferromagnetism in diluted magnetic semiconductor quantum wells

Physical review. B, Condensed matter (2000)

Byounghak Lee T. Jungwirth A. H. MacDonald

We present a mean field theory of ferromagnetism in diluted magnetic semiconductor quantum wells. When subband mixing due to exchange interactions between quantum well free carriers and magnetic impurities is neglected, analytic result can be obtained for the dependence of the critical temperature and the spontaneous magnetization on the distribution of magnetic impurities and the quantum well width. The validity of this approximate theory has been tested by comparing its predictions with those from numerical self-consistent field calculations. Interactions among free carriers, accounted for using the local-spin-density approximation, substantially enhance the critical temperature. We demonstrate that an external bias potential can tune the critical temperature through a wide range.

Magnetic semiconductor

Spontaneous magnetization

Exchange interaction

10.1103/physrevb.61.15606

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Citations (109)

Giant and Tunneling Magnetoresistance in Unconventional Collinear Antiferromagnets with Nonrelativistic Spin-Momentum Coupling

Physical Review X (2022)

Libor Šmejkal Anna Birk Hellenes Rafael González‐Hernández Jairo Sinova T. Jungwirth

Giant or tunneling magnetoresistance are physical phenomena used for reading information in commercial spintronic devices. The effects rely on a conserved spin current passing between a reference and a sensing ferromagnetic electrode in a multilayer structure. Recently, we have proposed that these fundamental spintronic effects can be realized in collinear antiferromagnets with staggered spin-momentum exchange interaction, which generates conserved spin currents in the absence of a net equilibrium magnetization. Here we elaborate on the proposal by presenting archetype model mechanisms for the antiferromagnetic giant and tunneling magnetoresistance effects. The models are based, respectively, on anisotropic and valley-dependent forms of the non-relativistic staggered spin-momentum interaction. Using first principles calculations we link these model mechanisms to real antiferromagnetic materials and predict a $\sim$100\% scale for the effects. We point out that besides the GMR/TMR detection, our models directly imply the possibility of spin-transfer-torques excitation of the antiferromagnets.

10.1103/physrevx.12.011028

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Citations (152)

Magneto-transport properties of (III,Mn)V diluted magnetic semiconductor structures

APS (2003)

T. Jungwirth Jairo Sinova Q. Niu Ramin Abolfath J. Kučera

Magnetic semiconductor

Magneto

Source

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Disorder and localization effects on the local spectroscopic and infrared optical properties ofGa1−xMnxAs

Physical Review B (2015)

Huawei Gao Cristian Cernov T. Jungwirth Jairo Sinova

We study numerically the influence of disorder and localization effects on the local spectroscopic characteristics and infrared optical properties of ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$. We treat the band structure and disorder effects at an equal level by using an exact diagonalization supercell simulation method. This method accurately describes the low-doping limit and gives a clear picture of the transition to higher dopings, which captures the localization effects inaccessible to other theoretical methods commonly used. Our simulations capture the rich in-gap localized states observed in scanning tunneling microscopy studies and reproduce the observed features of the infrared optical absorption experiments. We show clear evidence of a disordered-valence-band model for metallic samples in which (i) there is no impurity band detached from the valence band, (ii) the disorder tends to localize and pull states near the top of the valence band into the gap region, and (iii) the Fermi energy is located deep in the delocalized region away from the mobility edge. We identify localized states deep in the gap region by visualizing the probability distribution of the quasiparticles and connecting it to their respective participation ratios. The analysis of the infrared optical absorption data indicates that it does not have a direct relation to the nature of the states at the Fermi energy.

10.1103/physrevb.91.245201

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Citations (3)

Antiferromagnetic I-Mn-V semiconductors

arXiv (Cornell University) (2010)

T. Jungwirth V. Novák X. Martí M. Cukr F. Máca

After decades of research, the low Curie temperature of ferromagnetic semiconductors remains the key problem in the development of magnetic semiconductor spintronic technologies. Removing this roadblock might require a change of the field's basic materials paradigm by looking beyond ferromagnets. Recent studies of relativistic magnetic and magnetotransport anisotropy effects, which in principle are equally well present in materials with ferromagnetically and antiferromagnetically ordered spins, have inspired our search for antiferromagnetic semiconductors suitable for high-temperature spintronics. Since these are not found among the magnetic counterparts of common III-V or II-VI semi- conductors, we turn the attention in this paper to high N éel temperature I-II-V magnetic compounds whose electronic structure has not been previously identified. Our combined experimental and theoretical work on LiMnAs provides basic prerequisite for the systematic research of this class of materials by demonstrating the feasibility to grow single crystals of group-I alkali metal compounds by molecular beam epitaxy, by demonstrating the semiconducting band structure of the I-Mn-V's, and by analyzing their spin-orbit coupling characteristics favorable for spintronics.

10.48550/arxiv.1007.0177

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Citations (0)

Reorientation of Anisotropy in a Square Well Quantum Hall Sample

Physical Review Letters (2000)

W. Pan T. Jungwirth H. L. Störmer D. C. Tsui A. H. MacDonald

We have measured magnetotransport at half-filled high Landau levels in a quantum well with two occupied electric subbands. We find resistivities that are isotropic in perpendicular magnetic field but become strongly anisotropic at nu = 9/2 and 11/2 on tilting the field. The anisotropy appears at an in-plane field, B(ip) approximately 2.5 T, with the easy-current direction parallel to B(ip) but rotates by 90 degrees at B(ip) approximately 10 T and points now in the same direction as in single-subband samples. This complex behavior is in quantitative agreement with theoretical calculations based on a unidirectional charge density wave state model.

Landau quantization

Square (algebra)

Charge Density Wave

10.1103/physrevlett.85.3257

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Citations (31)