Geometrical magnetic frustration in rare-earth chalcogenide spinels

Lau, G. C.; Freitas, R. S.; Ueland, B. G.; Schiffer, P.; Cava, R. J.

doi:10.1103/physrevb.72.054411

Cited by 52 publications

(58 citation statements)

References 47 publications

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“…It is important to note that all photogalvanic effects addressed above are caused by the terms B (1) eff (k) and B SIA eff (k) in the effective magnetic field, which are first angular harmonics of ϑ k , see section 2.1. The rest cubic terms in the effective magnetic field B (3) eff (k) ∝ sin 3ϑ k , cos 3ϑ k do not result in the discussed photogalvanic currents, however, they modify the spin-splitting and may affect spin relaxation and the anisotropy of spin-flip Raman scattering [48,51,79,82,[157][158][159]. Consequently, photogalvanics based methods provide the information on the SIA/BIA terms given by Rashba constant α and renormalized Dresselhaus constantβ.…”

Section: Sige Qwsmentioning

confidence: 99%

Interplay of Rashba/Dresselhaus spin splittings probed by photogalvanic spectroscopy –A review

Ganichev

Golub²

2014

Physica Status Solidi (b)

206

205

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This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.The paper reviews the interplay of Rashba/Dresselhaus spin splittings in various two-dimensional systems made of zincblende III-V, wurtzite, and SiGe semiconductors. We discuss the symmetry aspects of the linear and cubic in electron wavevector spin splitting in heterostructures prepared on (001)-, (110)-, (111)-, (113)-, (112)-, and (013)-oriented substrates and address the requirements for suppression of spin relaxation and realization of the persistent spin helix state. In experimental part of the paper, we overview experimental results on the interplay of Rashba/Dresselhaus spin splittings probed by photogalvanic spectroscopy: The method based on the phenomenological equivalence of the linear-in-wavevector spin splitting and several photogalvanic phenomena.

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Section: Sige Qwsmentioning

confidence: 99%

Interplay of Rashba/Dresselhaus spin splittings probed by photogalvanic spectroscopy –A review

Ganichev

Golub²

2014

Physica Status Solidi (b)

206

205

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“…While this compound has been the subject of a number of investigations [20][21][22][27][28][29][30][31][32][33][34][35][36], the mechanism responsible for the selection of 4-k order has not been identified. Further, after fifteen years of research arXiv:1310.5146v1 [cond-mat.str-el] 18 Oct 2013 on the Tb 2 Ti 2 O 7 spin liquid candidate [37], evidence has recently begun accumulating that short-range magnetic correlations develop below T ∼ 0.4 K in the form of broad elastic neutron intensities at k = { 1 2 ) order is not unusual among the plethora of R 2 M 2 O 7 materials, or even AR 2 B 4 rare-earth spinels (A=Cd, Mg; B=S, Se and R is a rare-earth) [43][44][45].…”

Section: A) B)mentioning

confidence: 99%

Fluctuation-Driven Selection at Criticality in a Frustrated Magnetic System: The Case of Multiple-kPartial Order on the Pyrochlore Lattice

et al. 2015

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We study the problem of partially ordered phases with periodically arranged disordered (paramagnetic) sites on the pyrochlore lattice, a network of corner-sharing tetrahedra. The periodicity of these phases is characterized by one or more wave vectors k = { 1 2 1 2 1 2 }. Starting from a general microscopic Hamiltonian including anisotropic nearest-neighbor exchange, long-range dipolar interactions and second-and third-nearest neighbor exchange, we identify using standard mean-field theory (s-MFT) an extended range of interaction parameters that support partially ordered phases. We demonstrate that thermal fluctuations ignored in s-MFT are responsible for the selection of one particular partially ordered phase, e.g. the "4-k" phase over the "1-k" phase. We suggest that the transition into the 4-k phase is continuous with its critical properties controlled by the cubic fixed point of a Ginzburg-Landau theory with a 4-component vector order-parameter. By combining an extension of the Thouless-Anderson-Palmer method originally used to study fluctuations in spin glasses with parallel-tempering Monte-Carlo simulations, we establish the phase diagram for different types of partially ordered phases. Our results elucidate the long-standing puzzle concerning the origin of the 4-k partially ordered phase observed in the Gd2Ti2O7 dipolar pyrochlore antiferromagnet below its paramagnetic phase transition temperature. Highly frustrated magnetism is one of the paradigms of modern condensed matter physics [1]. In frustrated magnets, the combination of lattice geometry and competing interactions often leads to degenerate classical states. The degeneracies are generally accidental as they are not protected by the symmetries of the spin Hamiltonian. Yet, the degenerate states may be related by transformations that form an emergent symmetry group. Near a continuous phase transition, these approximate symmetries provide "organizing principles" in determining the critical properties by distinguishing relevant perturbations from irrelevant ones. In the most interesting case, the leading degeneracy-lifting perturbations, which may be relevant or irrelevant in the renormalization group sense, are thermal or quantum fluctuations -a phenomenon called order-by-disorder (ObD) [2][3][4][5]. The competition among diverse degeneracy-lifting effects can result in a modulated long-range ordered state at nonzero wave vector k, which may or may not be commensurate with the lattice [6][7][8][9][10][11][12]. In some cases, a number of superposed symmetryrelated k modes within the first Brillouin zone form a socalled multiple-k order [6,7,13,14]. A particular interesting form of such modulated magnetism is a partially ordered state (POS) with periodically arranged "paramagnetic" sites [15][16][17][18]. These fluctuating magnetic moments decimate a fraction of the energy-costly frustrated bonds while retaining an extensive entropy, hence lowering the free energy.In this Letter, we study the convergence of the aforementioned phenomena (emergent symmet...

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“…In fact, work by Lau and co-workers on the series CdR 2 X 4 (X ¼ S, Se) [11] has shown clear indications of geometrical frustration in these materials. Interestingly, the local environment of the rare-earth in the spinels is different to that in the pyrochlores.…”

mentioning

confidence: 99%

CdEr2Se4: A New Erbium Spin Ice System in a Spinel Structure

Lago¹,

Živković

Малкин

et al. 2010

Phys. Rev. Lett.

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Here we present a detailed study of the spinel CdEr 2 Se 4 and show it to be a new instance of spin ice, the first one in an erbium material and the first one in a spinel. Definitive experimental evidence comes from the temperature dependence of the magnetic entropy, which shows an excellent agreement with the predicted behavior for a spin ice state. Crystal field calculations demonstrate that the change in the local environment from that of the titanates completely alters the rare-earth anisotropy giving rise, in the case of Er 3þ , to the required Ising anisotropy, when The rare-earth (R) pyrochlores (R 2 M 2 O 7 ) have been found to display a rich variety of exotic magnetic behavior, a direct consequence of the impossibility, imposed by the geometry of the lattice, of finding a classical ground state by minimizing all pairwise exchange interactions. Theoretically, a system of antiferromagnetically coupled Heisenberg spins in a pyrochlore lattice should remain in a collective paramagnetic state as T ! 0 [1]. In practice, the macroscopic degeneracy can be lifted by lesser contributions to the spin Hamiltonian. In particular, the crystalline electric field (CEF) anisotropy term can dramatically alter the nature of the ground state, making it quasi specific to each rare-earth species. Thus, in the titanate series R 2 Ti 2 O 7 , the observed ground states in a zero applied field include nonconventional AFM states for the dipoleHeisenberg (R ¼ Gd [2]) and the XY (R ¼ Er [3,4]) systems, a spin liquid state (R ¼ Tb [5], half-way between Heisenberg and Ising), spin ice for the Ising Ho and Dy systems [6,7], and a dynamic disordered state (for Yb, with planar anisotropy [8][9][10]). The CEF anisotropy thus appears as the main cause for the rich phenomenology observed in the frustrated pyrochlores. But, at the same time, it constitutes a major limiting factor regarding the number of systems displaying a particular behavior as it effectively makes each R ion the only one of its kind.Normal spinels AR 2 X 4 constitute an alternative realm in which to look for exotic magnetism as the R ions occupying the octahedral sites in the structure form an identical pyrochlore sublattice to that in the titanates. In fact, work by Lau and co-workers on the series CdR 2 X 4 (X ¼ S, Se) [11] has shown clear indications of geometrical frustration in these materials. Interestingly, the local environment of the rare-earth in the spinels is different to that in the pyrochlores. This alters the CEF level scheme of the R ion and can potentially lead to completely different behavior for the same magnetic species in the two series despite the analogy in the overall geometry of the magnetic sublattice.In this Letter we show this to be the case. We present a detailed study of the cubic spinel CdEr 2 Se 4 (Fd 3m) and show that the change in the coordination environment of the Er 3þ ions from that of the pyrochlores Er 2 M 2 O 7 (M ¼ Ti, Sn) causes a change of the CEF anisotropy from planar to Ising, leading to spin ice behavior at low temperatures...

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Geometrical magnetic frustration in rare-earth chalcogenide spinels

Cited by 52 publications

References 47 publications

Interplay of Rashba/Dresselhaus spin splittings probed by photogalvanic spectroscopy –A review

Interplay of Rashba/Dresselhaus spin splittings probed by photogalvanic spectroscopy –A review

Fluctuation-Driven Selection at Criticality in a Frustrated Magnetic System: The Case of Multiple-kPartial Order on the Pyrochlore Lattice

CdEr2Se4: A New Erbium Spin Ice System in a Spinel Structure

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