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Kurniawan, Robi; Tanaka, Hidekazu; Takatsu, K.; Shiramura, W.; Fukuda, Tatsuo; Nojiri, Hiroyuki; Motokawa, M.

doi:10.1103/physrevlett.82.1281

Cited by 38 publications

(31 citation statements)

References 24 publications

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“…39,40) Recently, Ohta and his coworkers 41) have investigated the pressure dependence of the gap in KCuCl 3 up to 3.2 kbar by means of high-field and high-frequency ESR. Their result is in accordance with our result, as shown in Fig.…”

Section: 24)mentioning

confidence: 99%

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl₃

et al. 2006

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Magnetization and neutron elastic scattering measurements under a hydrostatic pressure were performed on KCuCl 3 , which is a three-dimensionally coupled spin dimer system with a gapped ground state. It was found that an intradimer interaction decreases with increasing pressure, while the sum of interdimer interactions increases. This leads to the shrinkage of spin gap. A quantum phase transition from a gapped state to an antiferromagnetic state occurs at P c % 8:2 kbar. For P > P c , magnetic Bragg reflections were observed at reciprocal lattice points equivalent to those for the lowest magnetic excitation at zero pressure. This confirms that the spin gap decreases and closes under applied pressure.

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Section: 24)mentioning

confidence: 99%

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl₃

et al. 2006

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“…3), detected by ESR measurements. 3 In the 1/4-plateau region, a ω 1 -mode increases linearly with the field, while the ω 2 -mode decreases and goes soft at H c2 . In this field region, each A dimer is fully polarized by the field, and is in the lowest lying triplet | ↑↑ , while the configuration of B dimer is dominated by the singlet component.…”

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“…2 For NH 4 CuCl 3 , Kurniawan et al performed ESR experiments which revealed that NH 4 CuCl 3 has a finite excitation gap in the plateau regions. 3 By studying specific heat, they found AF order already at zero field and suggested a phase diagram in finite fields containing three magnetically ordered phases. 4 The origin of magnetization plateaus has attracted much interest recently.…”

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confidence: 99%

“…In our model, we neglect other interactions, because they are expected to be small. The spin structure in the ordered phases of NH 4 CuCl 3 has not yet been determined, so we assume that its pattern is similar to field-induced staggered order of TlCuCl 3 and KCuCl 3 . Due to the modulation of the exchange couplings, the unit cell is larger than that of TlCuCl 3 and KCuCl 3 , with A and C dimers and two B dimers in the unit cell.…”

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Microscopic model for the magnetization plateaus inNH4CuCl3

Matsumoto

2003

Phys. Rev. B

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A simple model consisting of three distinct dimer sublattices is proposed to describe the magnetism of NH4CuCl3. It explains the occurrence of magnetization plateaus only at 1/4 and 3/4 of the saturation magnetization. The field dependence of the excitation modes observed by ESR measurements is also explained by the model. The model predicts that the magnetization plateaus should disappear under high pressure.PACS numbers: 75.30. Cr, NH 4 CuCl 3 , TlCuCl 3 , and KCuCl 3 are isostructual quantum spin systems consisting of two-leg ladders separated by NH + 4 , Tl + , and K + ions. The two-leg ladders are composed of Cu 2+ ions with spin S = 1/2 which interact antiferromagnetically (AF) through the Cl − ions. These compounds can be considered as coupled two-leg S = 1/2 Heisenberg AF spin ladders, and show various types of magnetization curves. Shiramura et al. found that NH 4 CuCl 3 has magnetization plateaus at 1/4 and 3/4 of the saturation moment, 1 while TlCuCl 3 and KCuCl 3 have no plateaus in their magnetization curves. 2 For NH 4 CuCl 3 , Kurniawan et al. performed ESR experiments which revealed that NH 4 CuCl 3 has a finite excitation gap in the plateau regions. 3 By studying specific heat, they found AF order already at zero field and suggested a phase diagram in finite fields containing three magnetically ordered phases. 4 The origin of magnetization plateaus has attracted much interest recently. For weakly interacting dimer systems, the ground state is a spin singlet liquid with only short-range correlations between spins, and the triplet excitations require a finite excitation energy. An excited gas of triplet magnons has two characteristic energies. 5 Exchange interactions cause the transfer of excited triplets between neighboring dimers leading to a form of kinetic energy. They also lead to a short range repulsion between triplets in addition to the hard core repulsion forbidding double occupancy of a dimer. The triplet excitations are split in an external magnetic field, and the energy of the lowest component can be driven through zero. When the kinetic energy is dominant, which is realized in TlCuCl 3 and KCuCl 3 , we have no plateaus in the magnetization curve. 2 In these case, antiferromagnetic order perpendicular to the field appears simultaneously with magnetization parallel to the field, creating field-induced magnetic order, 6 which can be interpreted as a condensation of the lowest lying magnon mode. 7,8,9,10,11,12,13,14,15 In contrast to these case, when the interaction energy dominates, magnetization plateaus can appear accompanied by a magnetic superlattice. 16 Such plateaus have been observed at a rational fraction of the saturation moment. 1,17 In SrCu 2 (BO 3 ) 2 , the frustrated form of the dimer lattice leads to a narrow bandwidth for triplet excitations and magnetization plateaus associated with a magnetic superlattice of localized triplets. 18,19 An unexpected feature of NH 4 CuCl 3 is the absence of a magnetization plateau at a value 1/2 of the saturation magnetization although this...

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“…Recently, Matsumoto [21] theoretically suggested that there are three distinct magnetic dimer sublattices with different exchange interactions in NH 4 CuCl 3 , in contrast to the isostructural KCuCl 3 and TlCuCl 3 , and reproduced well the magnetization plateaus and field dependence of the magnetic resonance frequencies observed in ESR measurements [22,23] by his model. Successive structural phase transitions which may indicate the creation of such distinct magnetic dimers have been observed at low temperatures by means of various kind of experiments [24,25,26,27,28] while the isostructural KCuCl 3 and TlCuCl 3 undergo no structural phase transitions at low temperature.…”

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C63/65u- andC35/

et al. 2009

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63/65 Cu-and 35/37 Cl-NMR experiments were performed to investigate triplet localization in the S = 1/2 dimer compound NH 4 CuCl 3 , which shows magnetization plateaus at one-quarter and three-quarters of the saturation magnetization. In 63/65 Cu-NMR experiments, signal from only the singlet Cu site was observed, because that from the triplet Cu site was invisible due to the strong spin fluctuation of onsite 3d-spins. We found that the temperature dependence of the shift of 63/65 Cu-NMR spectra at the singlet Cu site deviated from that of macroscopic magnetization below T = 6 K. This deviation is interpreted as the triplet localization in this system. From the 35/37 Cl-NMR experiments at the 1/4-plateau phase, we found the two different temperature dependences of Cl-shift, namely the temperature dependence of one deviates below T = 6 K from that of the macroscopic magnetization as observed in the 63/65 Cu-NMR experiments, whereas the other corresponds well with that of the macroscopic magnetization in the entire experimental temperature region. We interpreted these dependences as reflecting the transferred hyperfine field at the Cl site located at a singlet site and at a triplet site, respectively. This result also indicates that the triplets are localized at low temperatures. 63/65 Cu-NMR experiments performed at high magnetic fields between the one-quarter and three-quarters magnetization plateaus have revealed that the two differently oriented dimers in the unit cell are equally occupied by triplets, the fact of which limits the theoretical model on the periodic structure of the localized triplets.

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ESR Study of the Opening and Closing of the Field-Induced Gap inNH4CuCl3

Cited by 38 publications

References 24 publications

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl₃

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl₃

Microscopic model for the magnetization plateaus inNH4CuCl3

C63/65u- andC35/

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ESR Study of the Opening and Closing of the Field-Induced Gap inNH4CuCl3

Cited by 38 publications

References 24 publications

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl3

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl3

Microscopic model for the magnetization plateaus inNH4CuCl3

C63/65u- andC35/

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Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl₃

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl₃