Low-temperature magnetization of (Ga,Mn)As semiconductors

Jungwirth, T.; Mašek, J.; Wang, K. Y.; Edmonds, K. W.; Sawicki, M.; Polini, Marco; Sinova, Jairo; MacDonald, Allan H.; Campion, R. P.; Zhao, Lixia; Farley, N. R. S.; Johal, T. K.; Laan, G. van der; Foxon, C. T.; Gallagher, B. L.

doi:10.1103/physrevb.73.165205

Cited by 52 publications

(49 citation statements)

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“…In DMS, a small fraction of magnetic ions, usually Manganese 23 , is introduced into a semiconductor. While III-V compounds such as Ga 1−x Mn x As are typically p-doped 8 and can thus exhibit carrier-mediated ferromagnetism 24 , II-VI materials such as Cd 1−x Mn x Te are found to be intrinsic and paramagnetic due to the isoelectrical incorporation of the Mn impurities.A lot of theoretical works on DMS has been devoted to the understanding of structural properties [25][26][27][28][29][30] . But in many experiments, also the spin dynamics studied via optical pump-probe experiments is of interest 17,18,31 .…”

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Quantum kinetic equations for the ultrafast spin dynamics of excitons in diluted magnetic semiconductor quantum wells after optical excitation

2017

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Quantum kinetic equations of motion for the description of the exciton spin dynamics in II-VI diluted magnetic semiconductor quantum wells with laser driving are derived. The model includes the magnetic as well as the nonmagnetic carrier-impurity interaction, the Coulomb interaction, Zeeman terms, and the light-matter coupling, allowing for an explicit treatment of arbitrary excitation pulses. Based on a dynamics-controlled truncation scheme, contributions to the equations of motion up to second order in the generating laser field are taken into account. The correlations between the carrier and the impurity subsystems are treated within the framework of a correlation expansion. For vanishing magnetic field, the Markov limit of the quantum kinetic equations formulated in the exciton basis agrees with existing theories based on Fermi's golden rule. For narrow quantum wells excited at the 1s exciton resonance, numerical quantum kinetic simulations reveal pronounced deviations from the Markovian behavior. In particular, the spin decays initially with approximately half the Markovian rate and a non-monotonic decay in the form of an overshoot of up to 10 % of the initial spin polarization is predicted. I. INTRODCTIONThe idea behind the spintronics paradigm 1-4 is to combine state-of-the-art electronics based on carrier charge with the manipulation and control of the spin degree of freedom [5][6][7] . Diluted magnetic semiconductors (DMS)8-10 present an interesting subclass of semiconductors in this context because they can be easily combined with current semiconductor technology while at the same time providing a wide range of spin and magnetizationrelated effects and applications [11][12][13][14][15][16][17][18][19][20][21][22] . In DMS, a small fraction of magnetic ions, usually Manganese 23 , is introduced into a semiconductor. While III-V compounds such as Ga 1−x Mn x As are typically p-doped 8 and can thus exhibit carrier-mediated ferromagnetism 24 , II-VI materials such as Cd 1−x Mn x Te are found to be intrinsic and paramagnetic due to the isoelectrical incorporation of the Mn impurities.A lot of theoretical works on DMS has been devoted to the understanding of structural properties [25][26][27][28][29][30] . But in many experiments, also the spin dynamics studied via optical pump-probe experiments is of interest 17,18,31 . Theoretical descriptions of such experiments are less developed in the literature and are typically based on rateequation models [12][13][14]17,[31][32][33][34][35] , coinciding with Fermi's golden rule for vanishing magnetic field. However, a number of experiments have provided strong evidence that these models fail to reproduce some of the pertinent characteristics of the spin dynamics in DMS. Most notably, experimentally observed spin-decay rates are found to be a factor of 5 larger than the Fermi's golden rule result for spin-flip scattering of conduction band electrons at magnetic impurities 31 . Camilleri et al. 17 have argued that their optical experiments probe excitons rather than ...

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Quantum kinetic equations for the ultrafast spin dynamics of excitons in diluted magnetic semiconductor quantum wells after optical excitation

2017

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“…3e,f). Assuming 4.5 m B per Mn atom 18 (m B is the Bohr magneton), we can estimate the density N Mn of uncompesated Mn Ga moments from the magnetization data (see left y axis in Fig. 3e).…”

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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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“…In particular, spin-density waves appear to be the ground state in the case of 1D systems [84]. Another proposal involves canted ferromagnetism stemming from a non-scalar form of spin-spin interactions, brought about by spin-orbit coupling [85], though a large value of saturation magnetization in (Ga,Mn)As indicates that the effect is not large [86]. Finally, a competition between long-range ferromagnetic interactions and intrinsic short-range antiferromagnetic interactions [83] may affect the character of magnetic order [87].…”

Section: Effects Of Competing Magnetic Interactionsmentioning

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High Temperature Ferromagnetism and Nano-Scale Phase Separations in Diluted Magnetic Semiconductors and Oxides

Dietl

2007

Acta Phys. Pol. A

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In this paper the present understanding of the origin of ferromagnetic response that has been detected in a number of diluted magnetic semiconductors and diluted magnetic oxides at room temperature is outlined. It is argued that in these systems, owing to a typically small solubility of magnetic ions, crystallographic or chemical phase separation into regions with a large and a small concentration of magnetic component takes place. The ferromagnetic signatures then come from the regions with a large concentration of magnetic ions, which show non-zero spontaneous magnetization up to the blocking temperature, whose magnitude is proportional to the nanocrystal volume and magnetic anisotropy. Novel methods enabling a control of nano-assembling of magnetic nanocrystals in non-conducting matrices as well as possible functionalities of these spatially modulated magnetic systems are described. We also discuss phase separations into paramagnetic and ferromagnetic regions, which are driven by the Anderson-Mott localization and/or competing ferromagnetic and antiferromagnetic interactions. Finally, the question whether the high temperature ferromagnetism is possible in materials without magnetic ions is addressed.

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Low-temperature magnetization of (Ga,Mn)As semiconductors

Cited by 52 publications

References 50 publications

Quantum kinetic equations for the ultrafast spin dynamics of excitons in diluted magnetic semiconductor quantum wells after optical excitation

Quantum kinetic equations for the ultrafast spin dynamics of excitons in diluted magnetic semiconductor quantum wells after optical excitation

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

High Temperature Ferromagnetism and Nano-Scale Phase Separations in Diluted Magnetic Semiconductors and Oxides

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