Anomalous Magnetizations in Single Crystalline SrCu2(BO3)2

Kageyama, Hiroshi; Onizuka, Kenzo; Yamauchi, Touru; Ueda, Yutaka; Hane, S.; Mitamura, Hiroyuki; Goto, T.; Yoshimura, Kazuyoshi; Koyamada, Koji

doi:10.1143/jpsj.68.1821

Cited by 59 publications

(52 citation statements)

References 8 publications

(20 reference statements)

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“…J 2 /J 1 ≃ 0.6 [9]. As expected for this ratio SCBO has a dimerized singlet ground-state separated from the excited triplet states by a finite gap ∆ ≃ 35 K as seen in the magnetic susceptibility [10] or in inelastic neutron scattering [11]. From the latter it is also known that the triplet excitations are almost dispersionless, i.e the group velocity is very small, in agreement with theoretical calculations [12][13][14][15].…”

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confidence: 84%

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Strong Damping of Phononic Heat Current by Magnetic Excitations inSrCu2(BO3)2

et al. 2001

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Measurements of the thermal conductivity as a function of temperature and magnetic field in the 2D dimer spin system SrCu2(BO3)2 are presented. In zero magnetic field the thermal conductivity along and perpendicular to the magnetic planes shows a pronounced double-peak structure as a function of temperature. The low-temperature maximum is drastically suppressed with increasing magnetic field. Our quantitative analysis reveals that the heat current is due to phonons and that the double-peak structure arises from pronounced resonant scattering of phonons by magnetic excitations.During the last few years the thermal conductivity (κ) of low dimensional spin systems has attracted considerable interest [1][2][3][4][5][6]. One reason is that in these materials a large magnetic contribution κ mag to the heat current may be present as observed e.g. for the spin ladder material Sr 14−x Ca x Cu 24 O 41 [6]. Another reason is that the phononic heat current κ ph probes the spectrum of magnetic excitations as well as the spin-phonon coupling [3][4][5]. The latter is very important in some of the low dimensional spin systems, e.g. in the spin-Peierls compound CuGeO 3 [4,5]. Both issues, the magnetic contribution to the heat current as well as the interaction of the phonons with magnetic excitations, are to a large extent unexplored and not well understood.A material of particular interest in this context is SrCu 2 (BO 3 ) 2 (SCBO) [7]. The Cu 2+ ions form a quasi-2D spin system which is by virtue of the crystal geometry an experimental realization of the Shastry-Sutherland model [8]. In SCBO the intra-dimer and inter-dimer couplings are of magnitude J 1 ≃ 72 K and J 2 ≃ 43 K, i.e. J 2 /J 1 ≃ 0.6 [9]. As expected for this ratio SCBO has a dimerized singlet ground-state separated from the excited triplet states by a finite gap ∆ ≃ 35 K as seen in the magnetic susceptibility [10] or in inelastic neutron scattering [11]. From the latter it is also known that the triplet excitations are almost dispersionless, i.e the group velocity is very small, in agreement with theoretical calculations [12][13][14][15]. Thus, a sizeable κ mag is not expected for SCBO making this material a natural candidate to study the influence of magnetic excitations on κ ph . In this letter we present measurements of the thermal conductivity of SCBO along (κ a ) and perpendicular (κ c ) to the 2D spin planes in a large temperature (2.5-275 K) and magnetic field range (0-17 T). In zero field, both κ a and κ c show pronounced double-peak structures as a function of T . For both directions the low-T maximum is drastically suppressed by a magnetic field. We present a model based on a purely phononic thermal conductivity and explain the double-peak structure and its field dependence by strong damping of the phononic heat current due to resonant scattering of phonons by magnetic excitations. With the same parameters our model considerably improves the description of the magnetic field dependence of the specific heat of SCBO [16].For our study two samples of rectan...

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“…Using g ≈ 2.07 [10], our model reproduces the overall influence of the magnetic field very well. The high T maxima remain unchanged whereas the low T maxima are continuously suppressed.…”

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Strong Damping of Phononic Heat Current by Magnetic Excitations inSrCu2(BO3)2

et al. 2001

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“…[4] the gap to be ∆ ≈ 19 K, while from the NMR relaxation rate they obtained the gap about 30 K. Magnetization measurements 4 clarified the presence of a gapped spinsinglet ground state and a continuos transition to the gapless magnetic state at 20 T which corresponds to a gap of 30 K in a good agreement with the relaxation rate measurements. While early magnetization measurements in high fields revealed plateaus only at 1/4 and 1/8 of the saturated magnetization 4,6 , refined measurements have suggested 7 more plateaus at 1/3 and other values of magnetization.…”

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confidence: 91%

Effect of Dzyaloshinskii-Moriya interactions on the phase diagram and magnetic excitations of SrCu2(BO3)
Romhányi
¹
,
Totsuka
²
,
Penc
³

2011
Phys. Rev. B

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The orthogonal dimer structure in the SrCu2(BO3)2 spin-1/2 magnet provides a realization of the Shastry-Sutherland model. Using a dimer-product variational wave function, we map out the phase diagram of the Shastry-Sutherland model including anisotropies. Based on the variational solution, we construct a bond-wave approach to obtain the excitation spectra as a function of magnetic field. The characteristic features of the experimentally measured neutron and ESR spectra are reproduced, like the anisotropy induced zero field splittings and the persistent gap at higher fields.

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“…15,[26][27][28][29][30][31][32][33][34] To understand spin correlations at the atomic scale, however, requires inelastic neutron scattering experiments, which so far have been limited to the vicinity of the lower critical field H c1 . [35][36][37][38][39][40][41][42][43] By selecting a material, copper nitrate, with a suitable energy scale and utilizing high efficiency coldneutron instrumentation, we can provide a comprehensive set of data for the field and wave vector dependence of collective magnetic excitations in a system of interacting spin-1/2 dimers throughout the relevant field range.…”

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confidence: 99%

Magnons and continua in a magnetized and dimerized spin-12chain

et al. 2014

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We examine the magnetic field dependent excitations of the dimerized spin-1/2 chain, copper nitrate, with antiferromagnetic intra-dimer exchange J1 = 0.44(1) meV and exchange alternation α = J2/J1 = 0.26(2). Magnetic excitations in three distinct regimes of magnetization are probed through inelastic neutron scattering at low temperatures. At low and high fields there are three and two long-lived magnon-like modes, respectively. The number of modes and the anti-phase relationship between the wave-vector dependent energy and intensity of magnon scattering reflect the distinct ground states: A singlet ground state at low fields µ0H < µ0Hc1 = 2.8 T and an Sz = 1/2 product state at high fields µ0H > µ0Hc2 = 4.2 T. In the intermediate field regime, a continuum of scattering forhω ≈ J1 is indicative of a strongly correlated gapless quantum state without coherent magnons.

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Anomalous Magnetizations in Single Crystalline SrCu₂(BO₃)₂

Cited by 59 publications

References 8 publications

Strong Damping of Phononic Heat Current by Magnetic Excitations inSrCu2(BO3)2

Strong Damping of Phononic Heat Current by Magnetic Excitations inSrCu2(BO3)2

Effect of Dzyaloshinskii-Moriya interactions on the phase diagram and magnetic excitations of SrCu2(BO3)
Romhányi
¹
,
Totsuka
²
,
Penc
³

2011
Phys. Rev. B

Magnons and continua in a magnetized and dimerized spin-12chain

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Anomalous Magnetizations in Single Crystalline SrCu2(BO3)2

Cited by 59 publications

References 8 publications

Strong Damping of Phononic Heat Current by Magnetic Excitations inSrCu2(BO3)2

Strong Damping of Phononic Heat Current by Magnetic Excitations inSrCu2(BO3)2

Effect of Dzyaloshinskii-Moriya interactions on the phase diagram and magnetic excitations of SrCu2(BO3)Romhányi1, Totsuka2, Penc3 2011Phys. Rev. B

Magnons and continua in a magnetized and dimerized spin-12chain

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Anomalous Magnetizations in Single Crystalline SrCu₂(BO₃)₂

Effect of Dzyaloshinskii-Moriya interactions on the phase diagram and magnetic excitations of SrCu2(BO3)
Romhányi
¹
,
Totsuka
²
,
Penc
³

2011
Phys. Rev. B