Random fields in disordered magnetics with Jahn-Teller ions

Ivanov, M. A.; Mitrofanov, V. Ya.; Falkovskaya, L. D.; Fishman, A. Ya.

doi:10.1016/0304-8853(83)91040-5

Cited by 36 publications

(14 citation statements)

References 8 publications

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“…For low temperatures, C p approaches zero, following a strict T 2 dependence. In [21], it was shown that random fields can suppress OO and that in systems where OO is absent, the heat capacity follows C p / T 2 , just as observed here. Figure 1(c) shows the entropy for the polycrystals and single crystals as obtained by integrating C p T=T for 0:1 T 20 K. In the orbitally ordered system, the orbital entropy S orb approaches zero below the OO transition.…”

supporting

confidence: 56%

Orbital Freezing and Orbital Glass State inFeCr2S4

et al. 2005

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Low-temperature specific heat measurements and dielectric spectroscopy have been performed on polycrystalline and single-crystalline FeCr2S4, the single crystals showing a transition into a low-temperature orbital glass phase. The freezing of the orbital moments is revealed by a glasslike specific heat anomaly and by a clear relaxational behavior of the dielectric permittivity, exhibiting several hallmark features of glassy dynamics. The orbital relaxation dynamics continuously slows down over six decades in time, before at the lowest temperatures the glass transition becomes suppressed by quantum tunneling.

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supporting

confidence: 56%

Orbital Freezing and Orbital Glass State inFeCr2S4

et al. 2005

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“…5 ) is described by value of h, in the range of 30 K 5 lhol 5 40 K and = 0.2 MHz. These values of h, are in reasonable agreement with the characteristic values of low-symmetry field dispersion for spinel systems [14].…”

Section: (3)supporting

confidence: 85%

Supertransferred Hyperfine Fields at Nuclei of Diamagnetic Copper Ions in Chalcogenide Spinels Fe_1−xCu_xCr₂S₄

Fishman

Mitrofanov

Kovtun

et al. 1989

Physica Status Solidi (b)

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The NMR method is applied to study the local fields a t diamagnetic Cu+ ion nuclei in the magnetically ordered F1-,Cu,Cr2S, (0 5 5 5 0.8) system. Additional transferred hyperfine fields are revealed a t the Cu+ ion which are connected with orbital (pseudospin) moments of Fez+ ions. The obtained results are interpreted qualitatively. NMR-Methoden werden fiir die Untersuchung der Lokalfelder an diamagnetischen Cu+-Ionenkernen in dem magnetisch geordneten Fel -zCu,Cr2S, (0 5 x 5 0,s)-System benutzt. Zusatzliche ubertragene Hyperfeinfelder werden an Cu+-Ionen nachgewiesen, die mit Bahn-(Pseudospin)-Momenten von Fez+-Ionen verbunden sind. Die erhaltenen Ergebnisse werden qualitativ erklart. 1) Amundsen str. 101, SU-620819 Sverdlovsk, USSR. 2) R. Luxemburg str. 72, SU-340 114 Donetsk, USSR.

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“…by random strains was proposed previously [8], but the expected T 2 contribution to the specific heat [9] was not observed experimentally [3]. The orbital degeneracy's contribution to the specific heat and magnetic entropy have been verified experimentally [3].…”

mentioning

confidence: 69%

“…Numbers in parenthesis represent the degeneracy of each level. Second order SOC splits the lower 5 E doublet into 5 equally spaced levels separated by λ = 6(λ0 2 /∆CF ).by random strains was proposed previously [8], but the expected T 2 contribution to the specific heat [9] was not observed experimentally [3]. The orbital degeneracy's contribution to the specific heat and magnetic entropy have been verified experimentally [3].…”

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confidence: 69%

Singlet-Triplet Excitations and Long-Range Entanglement in the Spin-Orbital Liquid CandidateFeSc2S4

et al. 2015

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Theoretical models of the spin-orbital liquid (SOL) FeSc2S4 have predicted it to be in close proximity to a quantum critical point separating a spin-orbital liquid phase from a long-range ordered magnetic phase. Here, we examine the magnetic excitations of FeSc2S4 through timedomain terahertz spectroscopy under an applied magnetic field. At low temperatures an excitation emerges that we attribute to a singlet-triplet excitation from the SOL ground state. A threefold splitting of this excitation is observed as a function of applied magnetic field. As singlet-triplet excitations are typically not allowed in pure spin systems, our results demonstrate the entangled spin and orbital character of singlet ground and triplet excited states. Using experimentally obtained parameters we compare to existing theoretical models to determine FeSc2S4's proximity to the quantum critical point. In the context of these models, we estimate that the characteristic length of the singlet correlations to be ξ/(a/2) ≈ 8.2 (where a/2 is the nearest neighbor lattice constant) which establishes FeSc2S4 as a SOL with long-range entanglement.The search for ground states without classical analogs, e.g. quantum ground states, is a central focus of modern condensed matter physics. A zero temperature spin liquid would be a prime realization of such a state [1]. Such systems possess local moments, but, due to quantum fluctuations, typically enhanced due to geometric frustration, do not order even at zero temperature. They are proposed to have quantum mechanically entangled wavefunctions, with exotic fractionalized excitations. Orbital degrees of freedom can also be disordered by quantum fluctuations [2]. Systems with both spin and orbital fluctuations as well as spin-orbit coupling (SOC) have been proposed to form a "spin-orbital liquid" (SOL) ground state, characterized by entangled spin and orbital degrees of freedom but no long range order [3][4][5][6][7].Recent experiments have shown a SOL phase may exist in the geometrically frustrated A site cubic spinel compound FeSc 2 S 4 . A tetrahedral S 4 crystal field splits a 3d shell into an upper t 2 orbital triplet and a lower e orbital doublet. With Hund's coupling, an Fe 2+ ion in a tetrahedral environment assumes a high spin S = 2 configuration with a lower 5 E orbital doublet ground state and an upper 5 T 2 orbital triplet excited state (Fig. 1). The ground state's two-fold orbital degeneracy is associated with the freedom to place a hole in either e orbital. Although orbital degeneracy is often relieved by Jahn-Teller distortions, heat capacity experiments show no sign of orbital ordering down to 50 mK and the magnetic susceptibility displays essentially perfect Curie-Weiss behavior with θ CW = -45.1 K in the range from 15 -400K [3]. The possible removal of the ground state orbital degeneracy FIG. 1: (a) Energy levels of Fe 2+ ion in an S=2 configuration after tetrahedral crystal field splitting and first and second order SOC, without including lattice effects. Numbers in parenthesis represen...

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Random fields in disordered magnetics with Jahn-Teller ions

Cited by 36 publications

References 8 publications

Orbital Freezing and Orbital Glass State inFeCr2S4

Orbital Freezing and Orbital Glass State inFeCr2S4

Supertransferred Hyperfine Fields at Nuclei of Diamagnetic Copper Ions in Chalcogenide Spinels Fe_1−xCu_xCr₂S₄

Singlet-Triplet Excitations and Long-Range Entanglement in the Spin-Orbital Liquid CandidateFeSc2S4

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Random fields in disordered magnetics with Jahn-Teller ions

Cited by 36 publications

References 8 publications

Orbital Freezing and Orbital Glass State inFeCr2S4

Orbital Freezing and Orbital Glass State inFeCr2S4

Supertransferred Hyperfine Fields at Nuclei of Diamagnetic Copper Ions in Chalcogenide Spinels Fe1−xCuxCr2S4

Singlet-Triplet Excitations and Long-Range Entanglement in the Spin-Orbital Liquid CandidateFeSc2S4

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Supertransferred Hyperfine Fields at Nuclei of Diamagnetic Copper Ions in Chalcogenide Spinels Fe_1−xCu_xCr₂S₄