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Kofu, Maiko; Ueda, Hiroaki; Nojiri, Hiroyuki; Oshima, Yoshiteru; Zenmoto, T.; Rule, K. C.; Gerischer, S.; Lake, B.; Batista, Cristian D.; Ueda, Yutaka; Lee, S.-H.

doi:10.1103/physrevlett.102.177204

Cited by 47 publications

(74 citation statements)

References 20 publications

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“…12 Following Ref. 15 we assign modes 1 and 1' to the cooperative acoustic (n = 0) and optical modes (n = ±1) of the coupled dimers of different bilayers with eigenfrequencies = 5.14 meV in agreement with our experimental values. The observability of the singlet-triplet transitions 1, 1', and 3' implies an additional anisotropic contribution to the spin Hamiltonian, which mixes singlet and triplet states and relaxes the selection rule ∆S.…”

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confidence: 79%

“…The effective g-factor of 1.93(1) is almost constant below 70 K, and in good agreement with THz transmission spectra and previous reports. 9,15 When ∆H starts to increase strongly and reaches the order of magnitude of the resonance field above 70 K (see below), g-factor cannot be determined reliably anymore. The temperature dependence is described using ∆H = ∆H 0 +A exp (− 130 kOe, and a gap ∆/k B = 388 K. The exponential increase of the ESR linewidth indicates that the relaxation of the excited spins occurs via an Orbach process, 17 i.e.…”

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confidence: 99%

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Orbital fluctuations and orbital order below the Jahn-Teller transition in Sr3Cr2O<

Wang

Schmidt²,

Günther³

et al. 2011

Phys. Rev. B

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We report on the magnetic and phononic excitation spectrum of Sr3Cr2O8 determined by THz and infrared (IR) spectroscopy, and electron spin resonance (ESR) measurements across the Jahn-Teller transition, which is detected by specific-heat measurements to occur at TJT = 285 K. We identify the singlet-triplet excitations in the dimerized ground state and estimate the exchange couplings in the system. ESR absorptions were observed up to T * = 120 K with a linewidth ∝ exp (−∆/kBT ) and ∆/kB = 388 K indicating a phonon-mediated spin relaxation via the excited orbital state of the Cr e doublet in the orbitally ordered state. Upon entering the low-symmetry Jahn-Teller distorted phase below TJT , we find an extended regime T * < T < TJT where the IR active phonons change only gradually with decreasing temperature. This regime is associated with strong fluctuations in the orbital and lattice degrees of freedom in agreement with the loss of the ESR signal above T * . Using the measured magnetic and phononic excitation spectrum we model the orbital contribution to the specific heat and find the persistence of strong fluctuations far below TJT .PACS numbers: 78.30.-j,71.70.-d,76.30.-v,78.20.-e Orbital degrees of freedom (DOF) and their coupling to other DOF play an important role in understanding the physics in many transition-metal compounds including colossal magnetoresistive manganites, vanadates, and iron-based superconductors.1-3 Orbital ordering (OO) mechanisms, 4 collective orbital excitations, 5 and frustration effects in the orbital sector have attracted considerable attention and formed the research field of orbital physics. Exotic ground states such as orbital and spinorbital liquids have been explored both experimentally and theoretically.6 Orbital fluctuations play an important role in the formation of these states and may even induce a dimerization of spins via magnetoelastic coupling. 7Here we investigate the OO transition in the spingapped dimerized system Sr 3 Cr 2 O 8 . This compound has come into focus due to the occurrence of a field-induced magnon condensation.8,9 The room temperature crystal structure of Sr 3 Cr 2 O 8 was determined to be hexagonal with space group R3m.10 Each Cr 5+ ion with spin S = 1/2 is surrounded by an oxygen tetrahedron and couples antiferromagnetically to adjacent Cr 5+ ions along c direction, forming a spin singlet ground state at low temperatures. The tetrahedral crystal field splits the 3d levels into lower-lying doubly-degenerated e and triplydegenerated t orbitals. Thus, the Cr 5+ ions are JahnTeller (JT) active and a JT transition to a monoclinic structure with three twinned domains and space group C 2/c has been reported by neutron experiments to occur at 275 K.11,12 Primarily associated with the antiferrodistortive displacement of the apical oxygen ions this transition is suggested to be accompanied by the splitting of the e doublet into a lower-lying d 3z 2 −r 2 and excited d x 2 −y 2 orbital, and an antiferro-orbital ordering of d 3z 2 −r 2 orbitals. In addition, thi...

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confidence: 79%

mentioning

confidence: 99%

Orbital fluctuations and orbital order below the Jahn-Teller transition in Sr3Cr2O<

Wang

Schmidt²,

Günther³

et al. 2011

Phys. Rev. B

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“…with g = 1.94 which is only slightly anisotropic in these systems [15,16], paramagnetic background becomes more and more relevant so that a Brillouin term had to be included,…”

Section: Crystallographic Structurementioning

confidence: 99%

Structure and magnetic interactions in the solid solution Ba3−xSrxCr2O8

Grundmann

Schilling

Marjerrison

et al. 2013

Materials Research Bulletin

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“…The magnetic excitations consist of breaking a singlet into a spin-1 triplet which costs a finite amount of energy, the remaining interactions allow the triplet excitations to hop from dimer to dimer giving rise to a gapped dispersive mode [4,5]. A number of interesting physical phenomena have been observed in these materials such as field-induced transition to longrange magnetic order [6] that maps onto Bose-Einstein condensation [7], and strongly correlated behavior of the magnetic excitations at elevated temperature in contrast to the thermally induced decoherence typical of convention magnets [8,9].…”

Section: Introductionmentioning

confidence: 99%

Crystal growth, structure and magnetic properties of Ca₁₀Cr₇O₂₈

Balz

Lake

Reehuis

et al. 2017

J. Phys.: Condens. Matter

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A detailed diffraction study of Ca10Cr7O28 is presented which adds significant new insights into the structural and magnetic properties of this compound. A new crystal structure type was used where the a and b axes are doubled compared to previous models providing a more plausible structure where all crystallographic sites are fully occupied. The presence of two different valences of chromium was verified and the locations of the magnetic Cr 5+ and non-magnetic Cr 6+ ions were identified. The Cr 5+ ions have spin-1 /2 and form distorted kagome bilayers which are stacked in an ABC arrangement along the c axis. These results lay the foundation for understanding of the quantum spin liquid behavior in Ca10Cr7O28 which has recently been reported in [C. Balz et al., Nature Physics, 12, 942 (2016)].

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Magnetic-Field Induced Phase Transitions in a Weakly Coupleds=1/2Quantum Spin Dimer SystemBa3Cr2O8

Cited by 47 publications

References 20 publications

Orbital fluctuations and orbital order below the Jahn-Teller transition in Sr3Cr2O<

Orbital fluctuations and orbital order below the Jahn-Teller transition in Sr3Cr2O<

Structure and magnetic interactions in the solid solution Ba3−xSrxCr2O8

Crystal growth, structure and magnetic properties of Ca₁₀Cr₇O₂₈

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Magnetic-Field Induced Phase Transitions in a Weakly Coupleds=1/2Quantum Spin Dimer SystemBa3Cr2O8

Cited by 47 publications

References 20 publications

Orbital fluctuations and orbital order below the Jahn-Teller transition in Sr3Cr2O<

Orbital fluctuations and orbital order below the Jahn-Teller transition in Sr3Cr2O<

Structure and magnetic interactions in the solid solution Ba3−xSrxCr2O8

Crystal growth, structure and magnetic properties of Ca10Cr7O28

Contact Info

Product

Resources

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Crystal growth, structure and magnetic properties of Ca₁₀Cr₇O₂₈