Valence-Band Structure of the Ferromagnetic Semiconductor GaMnAs Studied by Spin-Dependent Resonant Tunneling Spectroscopy

Ohya, Shinobu; Muneta, Iriya; Hai, Pham Nam; Tanaka, Masaaki

doi:10.1103/physrevlett.104.167204

Cited by 46 publications

(51 citation statements)

References 22 publications

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“…Throughout the text we have provided arguments and references to relevant theory that supports an IB description for our data. Furthermore, the conclusion of the presence of a Mn-induced IB is supported by numerous previous studies of the electronic structure in FM Ga 1−x Mn x As 2, 10,22,28,29,35,56,[59][60][61] . Nonetheless, despite the experimental and theoretical support for an IB picture Ga 1−x Mn x As mentioned above, the experimental reality of the precise degree of separation between, and "mixing" of, impurity states and valence states remains unresolved.…”

Section: Discussionsupporting

confidence: 72%

“…Nonetheless, despite the experimental and theoretical support for an IB picture Ga 1−x Mn x As mentioned above, the experimental reality of the precise degree of separation between, and "mixing" of, impurity states and valence states remains unresolved. Analysis of resonant tunneling experiments has supported a strictly detached IB with remarkably little exchange splitting of the VB 29,61 . The interpretation of these tunneling data, however, has not been universally accepted (see Ref.…”

Section: Discussionmentioning

confidence: 95%

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Ferromagnetism and infrared electrodynamics of Ga1−xMnxAs

et al. 2013

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We report on the magnetic and the electronic properties of the prototype dilute magnetic semiconductor Ga1−xMnxAs using infrared (IR) spectroscopy. Trends in the ferromagnetic transition temperature TC with respect to the IR spectral weight are examined using a sum-rule analysis of IR conductivity spectra. We find non-monotonic behavior of trends in TC with the spectral weight to effective Mn ratio, which suggest a strong double-exchange component to the FM mechanism, and highlights the important role of impurity states and localization at the Fermi level. Spectroscopic features of the IR conductivity are tracked as they evolve with temperature, doping, annealing, As-antisite compensation, and are found only to be consistent with an Mn-induced IB scenario. Furthermore, our detailed exploration of these spectral features demonstrates that seemingly conflicting trends reported in the literature regarding a broad mid-IR resonance with respect to carrier density in Ga1−xMnxAs are in fact not contradictory. Our study thus provides a consistent experimental picture of the magnetic and electronic properties of Ga1−xMnxAs.

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Section: Discussionsupporting

confidence: 72%

Section: Discussionmentioning

confidence: 95%

Ferromagnetism and infrared electrodynamics of Ga1−xMnxAs

et al. 2013

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“…Our RIXS results show that the dominant charge transferred states are the trivalent Mn 3+ ground state and indicates the presence of a ligand hole bound to the Mn configuration. This arrangement will significantly reduce ionized impurity scattering and support the presence of quantum states in Ga 1−x Mn x As quantum wells observed by resonant tunneling spectroscopy [10,34].…”

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confidence: 53%

Electronic Excitations of a Magnetic Impurity State in the Diluted Magnetic Semiconductor (Ga,Mn)As

et al. 2014

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The electronic structure of doped Mn in (Ga,Mn)As is studied by resonant inelastic X-ray scattering (RIXS). From configuration-interaction cluster-model calculations, the line shapes of the Mn L3 RIXS spectra can be explained by d-d excitations from the Mn 3+ ground state, dominated by charge-transferred states, rather than a Mn 2+ ground state. Unlike archetypical d-d excitation, the peak widths are broader than the experimental energy resolution. We attribute the broadening to a finite lifetime of the d-d excitations, which decay rapidly to electron-hole pairs in the host valence and conduction bands through hybridization of the Mn 3d orbital with the ligand band.PACS numbers: 75.50. Pp, 78.70.Ck, 78.70.En A diluted magnetic semiconductor (DMS), in which a host semiconductor is doped with a low concentrations of magnetic ions, is a material of interest for spintronics research. In particular, ferromagnetic DMSs have attracted considerable attention because the itinerant carriers are considered to mediate the magnetic interaction between doped ions [1,2]. This type of magnetism is called "carrier-induced ferromagnetism" and enables the possibility of manipulating both electronic charge and spin degrees of freedom. III-V based DMS Ga 1−x Mn x As is an archetypical ferromagnetic DMS and has been studied from both fundamentally and in applications as a ferromagnetic DMS [3]. Spintronic devices using Ga 1−x Mn x As have been fabricated and their effectiveness has been demonstrated [4,5], although the Curie temperature (T C ) of Ga 1−x Mn x As is below room temperature (T C < 200 K).Understanding the mechanism of ferromagnetism in Ga 1−x Mn x As is strongly desirable to develop DMS for application in spintronic devices. Several physical models of the ferromagnetism have been proposed, e.g., the Zener p-d exchange model [1,6,7], the Mn 3d impurity band model [8][9][10], and the magnetic polaron model [11,12]. These models depend on the localization of hole carriers around the Mn ions, the energy position of the Mn 3d states, and the strength of hybridization between the Mn 3d orbital and the ligand band. To obtain a fundamental understanding of ferromagnetism, it is essential to know the Mn 3d electronic configurations in the ground state. If the valence state of Mn in the ground state is divalent (Mn 2+ ), the Mn ion acts as an acceptor supplying a hole to the host GaAs, supporting the Zener p-d exchange model. Thus, the electronic structure of Mn 3d ions in Ga 1−x Mn x As has been intensively investigated experimentally [10,[13][14][15]. However, the presence of divalent (Mn 2+ ) or trivalent (Mn 3+ ) states has not been conclusively determined, and the degree of the localization of the Mn 3d states remains a matter of dispute.In this Letter, to address the electronic structure of the doped Mn ions, we report the results of Mn L 3 Xray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) measurements of Ga 1−x Mn x As (x = 0.04). RIXS is a powerful tool to investigate electronic excitatio...

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“…We found that the following two ways are effective to increase T C and to enhance resonant tunneling to a certain degree. 51 One is to reduce the QW thickness for inducing stronger quantization, and the other is to use paramagnetic AlMnAs as an upper tunnel barrier of the GaMnAs QW. As described above, we found that T C of the lower GaMnAs layer can be increased to 60-70 K even when its thickness is thin (2 nm) by using a paramagnetic AlMnAs tunnel barrier in the GaMnAs single-barrier MTJ structures.…”

Section: Enhanced Resonant Tunneling and Tmr In Rtds With A Thin Gamnmentioning

confidence: 99%

Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport

Tanaka

Ohya

Hai

2014

Applied Physics Reviews

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Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMS), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose, and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As, and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (InFe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

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Valence-Band Structure of the Ferromagnetic Semiconductor GaMnAs Studied by Spin-Dependent Resonant Tunneling Spectroscopy

Cited by 46 publications

References 22 publications

Ferromagnetism and infrared electrodynamics of Ga1−xMnxAs

Ferromagnetism and infrared electrodynamics of Ga1−xMnxAs

Electronic Excitations of a Magnetic Impurity State in the Diluted Magnetic Semiconductor (Ga,Mn)As

Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport

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