On the nature of ferromagnetism in diluted magnetic semiconductors: GaAs:Mn

Krstajić, P. M.; Иванов, В. А.; Peeters, F. M.; Fleurov, V.; Kikoin, K.

doi:10.1209/epl/i2003-00224-x

Cited by 37 publications

(39 citation statements)

References 31 publications

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“…Recently, a contradicting hypothesis, with the Fermi level localized within the 3d-Mn impurity states, is discussed by the experimental group 27 , and followed by a theoretical work 28 with similar conclusions to earlier publication 29 . These works examine the double-exchange mechanism as possible in (Ga,Mn)As.…”

Section: Brief Summary Of Earlier Studiesmentioning

confidence: 66%

Hole -character and delocalization in (Ga,Mn)As revised with pSIC and MLWF approaches – Newly found spin-unpolarized gap states of s-type below 1 of Mn

Milowska

Wierzbowska

2014

Chemical Physics

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Hole sp 3 -character and delocalization in (Ga,Mn) The dilute magnetic semiconductor (Ga,Mn)As is ferromagnetic in accordance with the p-d Zener model. Hole density function (HDF) localization has been previously studied by means of the density functional theory (DFT) and non-standard DFT methods; however not for dopings near 1%. We have revised (Ga,Mn)As using the DFT with the pseudopotential self-interaction correction (pSIC) and maximally-localized Wannier functions (MLWFs), which show the sp 3 character of a HDF. Nature of HDF is extended -for low dopings and the pSIC, 70% of the HDF is located within the inter-impurities region, and contribution of the 3d-Mn states is 3-5% for 1-3% of Mn with the pSIC, and 11% with the DFT. We found that for dopings below 1%, the spin-unpolarized s-type impurity states segregate from the conduction band to the energy gap -in contrast to earlier publications. This implies that donor co-doped dilute samples would be both insulating and nonmagnetic.

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Section: Brief Summary Of Earlier Studiesmentioning

confidence: 66%

Hole -character and delocalization in (Ga,Mn)As revised with pSIC and MLWF approaches – Newly found spin-unpolarized gap states of s-type below 1 of Mn

Milowska

Wierzbowska

2014

Chemical Physics

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“…Indirect RKKY 17 , superexchange and double exchange 3 interactions between magnetic ions may be derived microscopically from the multisite generalization of the Anderson model. 18 The Hamiltonian of this model reads…”

Section: Model Of Dilute Magnetic Oxidementioning

confidence: 99%

“…Since no spin-flip occurs in the course of the exchange, the spin index may be omitted in the Hamiltonian (5), (8), (9). This energy gain is given by the following equation 3,25 …”

Section: Microscopic Theory Of Superexchange In Dmdmentioning

confidence: 99%

“…It was shown recently that the kinematic exchange interaction (specific version of superexchange between localized Mn moments via empty valence states of the host material) arises in p-type III-V DMS. 3 This mechanism works together with the RKKY interaction because of the noticeable hybridization between d-electrons of Mn ions and p-holes near the top of the valence band. Both mechanisms are characterized by a direct proportionality between the carrier concentration and Curie temperature T C .…”

Section: Introductory Notesmentioning

confidence: 99%

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Superexchange in dilute magnetic dielectrics: Application to(Ti,Co)O2

Kikoin

Fleurov

2006

Phys. Rev. B

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We extend the model of ferromagnetic superexchange in dilute magnetic semiconductors to the ferromagnetically ordered highly insulating compounds (dilute magnetic dielectrics). The intrinsic ferromagnetism without free carriers is observed in oxygen-deficient films of anatase TiO 2 doped with transition metal impurities in cation sublattice. We suppose that ferromagnetic order arises due to superexchange between complexes [oxygen vacancies + magnetic impurities], which are stabilized by charge transfer from vacancies to impurities. The Hund rule controls the superexchange via empty vacancy related levels so that it becomes possible only for the parallel orientation of impurity magnetic moments. The percolation threshold for magnetic ordering is determined by the radius of vacancy levels, but the exchange mechanism does not require free carriers. The crucial role of the non-stoichiometry in formation of the ferromagnetism makes the Curie temperatures extremely sensitive to the methods of sample preparation. * Email:fleurov@post.tau.ac.il. Among the most salient features of magnetism in dilute ferromagnetic oxides one should mention an extreme sensitivity of the magnetic order to the growth and annealing conditions. 5, 8 We believe that this is an integral feature of magnetism in these materials, and the ferromagnetic ordering with high T C is mediated by intrinsic or extrinsic defects, which form complexes with magnetic dopants. Such point of view is supported by recent experimental studies of Co-doped 9 and Cr-doped 10 TiO 2 . It was noticed, in particular, that in the most perfect (Ti, Cr)O 2 crystals the hysteresis loop at a given temperature is essentially less distinct than in 'bad quality' samples. 10 Besides, the enormous scatter of effective magnetic moment per cation is observed in all ferromagnetic oxides, and the concentration of magnetic dopants lies far below the percolation threshold x c associated with the nearest-neighbor cation coupling. 8 Basing on these facts, one concludes that non-magnetic defects are also involved in formation of the localized magnetic moments. They influence their magnitude and localization, and this influence is sensitive to the growth and annealing regimes.Recent theories of magnetism in n-type dilute magnetic oxides appeal to magnetic polarons as mediators of indirect exchange between magnetic dopants. 8,11 In this case the extrinsic defects are donor impurities, which donate free electrons occupying the bottom of conduction band. These electrons form shallow spin-polarized polaronic states due to strong exchange with the localized magnetic moments of transition metal dopants. A large radius of these states makes the polaronic percolation threshold essentially lower than x c .One should note, however, that the carrier concentration in these compounds is vanishingly small, and that is why they have been proposed to be called dilute magnetic dielectrics (DMD). 9 It means that we need now to find an exchange mechanism, which works in the case of really insulating ox...

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“…Among mechanisms leading to the ferromagnetic ordering of magnetic impurity spins various forms of their indirect interaction, induced by mobile charge carriers, are considered: RKKY-exchange [6], kinematic exchange [7,8], etc. [7].…”

Section: Mean Field Approachmentioning

confidence: 99%

Amplification of the induced ferromagnetism in diluted magnetic semiconductor

Meĭlikhov

Farzetdinova

2009

Physics Letters A

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Magnetic properties of the planar structure consisting of a ferromagnetic metal and the diluted magnetic semiconductor are considered (by the example of the structure Fe/Ga(Mn)As, experimentally studied in [1]). In the framework of the mean field theory, we demonstrate the presence of the significant amplification of the ferromagnetism, induced by the ferromagnetic metal in the nearinterface semiconductor area, due to the indirect interaction of magnetic impurities. This results in the substantial expansion of the temperature range where the magnetization in the boundary semiconductor region exists, that might be important for possible practical applications.

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On the nature of ferromagnetism in diluted magnetic semiconductors: GaAs:Mn

Cited by 37 publications

References 31 publications

Hole -character and delocalization in (Ga,Mn)As revised with pSIC and MLWF approaches – Newly found spin-unpolarized gap states of s-type below 1 of Mn

Hole -character and delocalization in (Ga,Mn)As revised with pSIC and MLWF approaches – Newly found spin-unpolarized gap states of s-type below 1 of Mn

Superexchange in dilute magnetic dielectrics: Application to(Ti,Co)O2

Amplification of the induced ferromagnetism in diluted magnetic semiconductor

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