Magneto-optical investigations of Eu-based diluted magnetic lead chalcogenides

Geist, F.; Herbst, W.; Mejía‐García, C.; Pascher, H.; Rupprecht, R.; Ueta, Y.; Springholz, G.; Bauer, G.; Tacke, M.

doi:10.1103/physrevb.56.13042

Cited by 27 publications

(18 citation statements)

References 41 publications

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“…[3][4][5][6] Pb 1Ϫx Eu x Te has been investigated by magnetooptics only in the low concentration range (xϽ0.06). 7 The analysis of magnetization [8][9][10] (xр0.32) and of magnetization steps 11 (xр0.06) in high-magnetic fields has given information about the distribution of Eu atoms and their mutual magnetic exchange interaction. The electronic band structure and the magnetooptical properties of the binary material PbTe are well known.…”

Section: Introductionmentioning

confidence: 99%

Interband Faraday and Kerr rotation and magnetization ofPb1−xEuxTein the con

et al. 1999

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Faraday and magneto-optical Kerr effect has been used for the investigation of the band alignment as well as of the magnetic properties of epitaxial layers of the ternary alloy system Pb 1Ϫx Eu x Te (0рxр1) grown on BaF 2 substrates. Due to the wide range of transition energies (0.19 eVрE g р2.25 eV) the experiments had to be performed in the spectral range from midinfrared to visible light. Data were collected at temperatures between 1.8 and 250 K and in magnetic fields up to 7 T. Concomitant magnetization measurements (B ϭ1 T) were performed with a superconducting quantum interference device ͑SQUID͒ magnetometer and compared with measurements of the x dependence of the Verdet constant. The variation of the fundamental absorption gap with Eu content can be understood in terms of the relative energetic position of PbTe-related band edges and Eu 4 f and 5d levels: ⌬E g /⌬xϭ4.48 eV for xϽ0.06; ⌬E g /⌬xϭ2.03 eV for 0.06ϽxϽ0.6. For xϾ0.8, the electronic transitions are identified to be EuTe-like. The most striking feature is a sign reversal of Verdet's constant around xϭ0.15, which is attributed to a crossover of Faraday rotation caused by band electrons ͑holes͒ and interacting pairs of magnetic ions and a metal-insulator transition. An antiferromagnetic phase transition is observed for xϾ0.8 in magneto-optics as well as in SQUID magnetometry.

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Section: Introductionmentioning

confidence: 99%

Interband Faraday and Kerr rotation and magnetization ofPb1−xEuxTein the con

et al. 1999

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“…The research concerns, in particular, magnetooptical studies of Pb1-x Eux Se and Pb1-x ΕuxΤe layers and PbΤe-Pb1-x Εux Te multiple quantum wells [7,8]. The application f the powerful coherent anti-Stokes Raman scattering (CARS) technique provides very detailed information on the band structure parameters.…”

Section: Rare-earth Ions Based Iv-vi Semimagnetic Semiconductorsmentioning

confidence: 99%

IV-VI Semimagnetic Semiconductors: Recent Developments

Story

1998

Acta Phys. Pol. A

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“…For each Dirac point, approximate explicit forms of the the wavefunctions may be constructed [25], which can be written as eigenstates of a mirror operatorσ 1 with eigenvalues ±1. Projection of H bulk onto these surface states allows us to construct effective Hamiltonians in the vicinity of each Dirac point.Magnetic Impurities and Surface Hamiltonians -It has long been known that metals in the (Sn/Pb)Te class [29][30][31][32][33][34][35][36][37], may be doped with magnetic ions which in some circumstances order ferromagnetically at low temperature. In these systems the magnetic ions enter substitutionally for Sn/Pb atoms, and the coupling of the magnetic moments with the conduction electrons can be understood rather well using an s−d model [38], H sd = J i S(r i )· s i , where s i represents an impurity spin at location r i and S(r i ) is the conduction electron spin density [39].…”

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Surface magnetism in topological crystalline insulators

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We study topological crystalline insulators doped with magnetic impurities, in which ferromagnetism at the surface lowers the electronic energy by spontaneous breaking of a crystalline symmetry. The number of energetically equivalent groundstates is sensitive to the crystalline symmetry of the surface, as well as the precise density of electrons at the surface. We show that for a SnTe model in the topological state, magnetic states can have two-fold, six-fold symmetry, or eight-fold degenerate minima. We compute spin stiffnesses within the model to demonstrate the stability of ferromagnetic states, and consider their ramifications for thermal disordering. Possible experimental consequences of the surface magnetism are discussed.PACS numbers: 73.20. At,75.70.Rf,75.30.Gw Introduction -Topological crystalline insulators (TCI's) are a class of materials in which the energy bands can host non-trivial topology protected by a crystalline symmetry [1]. These systems support surface states [2] which remain gapless provided the crystal symmetry is unbroken, and are believed to present themselves in (Sn,Pb)Te and related alloys [3][4][5][6][7][8]. Interesting effects may arise when the symmetry protecting a topological band structure is broken. In topological insulators protected by time-reversal symmetry (TRS), magnetic impurities on a surface break this symmetry and form collective states [9][10][11][12][13], which may be understood in terms of a gap opening in the surface spectrum [14].In contrast, TCI's are not protected by TRS, so the loss of this symmetry does not by itself energetically favor ordering of magnetic moments [15,16]. However, a uniform magnetization can undermine one or more relevant crystalline symmetries [17,18]. Indeed, the most common such symmetry is reflection across a mirror plane, of which there can be several. We show below that spontaneous surface magnetization opens a maximal gap when oriented along axes dictated by the bulk symmetries of the system. For a generic surface with a single mirror plane, there are two surface Dirac points at different momenta and energies [19], and in such cases at low temperature this results in a metallic, Ising-like ferromagnet, with the easy axis determined by the chemical potential µ. Importantly, the number of degenerate low-energy directions is enhanced for surfaces with further symmetries. Rotational symmetries in particular yield multiple mirror planes, and connect distinct surface Dirac cones to one another, yielding a multiplicity of easy axis directions. For sufficiently high symmetry, all the surface Dirac points may be related by symmetry operations, resulting in a fully gapped surface spectrum and a large number of groundstate orientations.To illustrate this physics, we present detailed calculations for the (111) surface of (Sn,Pb)Te [8,[20][21][22], using a known model Hamiltonian [3,23]. The (111) surface states are characterized in this system by four surface Dirac points, one at theΓ point and one at each of three Fig. 1(a).] When the system...

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Magneto-optical investigations of Eu-based diluted magnetic lead chalcogenides

Cited by 27 publications

References 41 publications

Interband Faraday and Kerr rotation and magnetization ofPb1−xEuxTein the con

Interband Faraday and Kerr rotation and magnetization ofPb1−xEuxTein the con

IV-VI Semimagnetic Semiconductors: Recent Developments

Surface magnetism in topological crystalline insulators

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