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Nakagawa, N.; Yamada, Takafumi; Akioka, K.; Okubo, Susumu; Kimura, Shojiro; Ohta, H.

doi:10.1023/a:1022511405901

Cited by 66 publications

(21 citation statements)

References 23 publications

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“…The ESR experiments were performed on a cavity spectrometer providing frequency range of 60-100 GHz and magnetic field up to 7 T (GPI, Moscow). Experiments at higher frequencies 100-360 GHz using a 30 T pulsed magnet were carried out at Kobe University with a quasioptical setup operating in reflection mode [45]. The magnetic field for all experiments was aligned along the [110] direction of the crystal.…”

Section: Resultsmentioning

confidence: 99%

Magnetic field dependence of the neutron spin resonance inCeB6

et al. 2016

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In zero magnetic field, the famous neutron spin resonance in the f-electron superconductor CeCoIn 5 is similar to the recently discovered exciton peak in the nonsuperconducting CeB 6 . A magnetic field splits the resonance in CeCoIn 5 into two components, indicating that it is a doublet. Here we employ inelastic neutron scattering (INS) to scrutinize the field dependence of spin fluctuations in CeB 6 . The exciton shows a markedly different behavior without any field splitting. Instead, we observe a second field-induced magnon whose energy increases with field. At the ferromagnetic zone center, however, we find only a single mode with a nonmonotonic field dependence. At low fields, it is initially suppressed to zero together with the antiferromagnetic order parameter, but then reappears at higher fields inside the hidden-order phase, following the energy of an electron spin resonance (ESR). This is a unique example of a ferromagnetic resonance in a heavy-fermion metal seen by both ESR and INS consistently over a broad range of magnetic fields. PACS numbers: 71.27.+a, 76.50.+g, 78.70.Nx, 76.30.Kg INTRODUCTIONThe observation of neutron spin resonance within a broad range of materials, in particular high-T c cuprates [1], iron pnictides [2,3], and heavy-fermion superconductors [4][5][6], is recognized as an indicator of unconventional superconductivity. It was shown that sign-changing gap symmetry can lead to the existence of resonance behavior [7][8][9][10]. Of particular interest are inelastic neutron scattering (INS) results obtained on CeCoIn 5 , where a sharp resonance peak was observed within the superconducting phase [5,[11][12][13]. At first glance similar peaks were found in the antiferromagnetic (AFM) superconductor UPd 2 Al 3 [14,15], as well as in the normal state of the heavy-fermion metal YbRh 2 Si 2 [16], where superconductivity was recently discovered below ∼ 2 mK [17]. Another striking example of a resonant mode is given by the well known nonsuperconducting heavyfermion antiferromagnet CeB 6 [18,19]. The microscopic origins of such resonant magnetic excitations persisting in f-electron systems either with or without superconductivity may well differ among materials and are still hotly debated.The application of an external magnetic field may help to unmask the differences between these various excitations. For instance, among f-electron compounds, a weak quasielastic signal gives rise to a field-induced ferromagnetic (FM) excitation in CeRu 2 Si 2 [20]. In YbRh 2 Si 2 , two incommensurate excitation branches merge into a commensurate FM resonance whose energy scales linearly with magnetic field [16], whereas in UPd 2 Al 3 the energy gap initially remains almost constant inside the superconducting phase, but starts following a monotonic linear dependence at higher magnetic fields [14]. The sharp resonance in CeCoIn 5 splits into a Zeeman doublet [11] rather than a theoretically predicted triplet [21], whereas in Ce 1−x La x B 6 the magnetic field reportedly leads to a crossover from an itinerant to ...

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Section: Resultsmentioning

confidence: 99%

Magnetic field dependence of the neutron spin resonance inCeB6

et al. 2016

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“…The details of our high field ESR system can be found in refs. [15][16][17][18]. Since the synthesis of a single crystal is very difficult, we used the natural single crystal mineral azurite (Cu 3 (CO 3 ) 2 (OH) 2 ) for the measurements.…”

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High Field ESR Study of theS=1/2 Diamond-Chain Substance Cu₃(CO₃)₂(OH)₂up to the Magnetization Plateau Region

et al. 2003

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High field ESR measurements of Cu 3 (CO 3 ) 2 (OH) 2 have been performed in the frequency region from 50 to 900 GHz and in the temperature region from 1.8 to 265 K using the pulsed magnetic field up to 36 T. The large g-shifts below 23 K and the characteristic temperature dependence of the linewidth are discussed in connection with the two maxima of magnetic susceptibility observed at 5 and 23 K. Our ESR results together with the magnetization and theoretical results suggest that the ground state of the system is in the spin fluid (SF) phase at low field and low temperature. From the frequency-field dependence measurements at 1.8 K, the direct transition, which is closely related to the magnetization plateau from 16 to 26 T at 1.5 K, is observed for the first time. The observed frequency-field diagram suggests that the exchange interaction in the dimer is estimated to be about 50 K (1057 GHz). Recently, the study of quantum spin systems with competing interactions, that is, frustration and quantum fluctuation, has attracted great interest. The diamond chain system, as shown in Fig. 1(a), is one of such systems, and it has attracted much theoretical interest, particularly after the suggestion by Ishii et al. that Cu 3 Cl 6 (H 2 O) 2 Á2H 8 C 4 SO 2 may be the model substance for the S ¼ 1=2 distorted diamond chain with the spin gap.1) Takano et al. studied the S ¼ 1=2 diamond chain model in the case of J 1 ¼ J 3 , and showed that the ground state is in the ferrimagnetic (FRI), tetramer-dimer (TD) and dimer-monomer (DM) phases for J 2 =J 1 < 0:909, 0:909 < J 2 =J 1 < 2 and 2 < J 2 =J 1 , respectively.2) It was extended to the S ¼ 1=2 distorted diamond chain model with J 1 , J 2 and J 3 , as shown in Fig. 1(a) by Okamoto et al. and Tonegawa et al., and the ground state phase diagram in the case of H ¼ 0, composed of ferrimagnetic (FRI), dimerized (D) and spin fluid (SF) phases as schematically shown in Fig. 1(b), were determined.3,4) It turned out that the TD and DM states were special cases of the twofold degenerate D and SF states, respectively. Tonegawa et al. also studied the magnetization curve numerically. 4,5) However, it turned out recently that the compound assumed to be Cu 3 Cl 6 -(H 2 O) 2 Á2H 8 C 4 SO 2 was actually Cu 2 Cl 4 Á2H 8 C 4 SO 2 which can be described by the S ¼ 1=2 double-spin chain model. 6)Therefore, the model substance for the S ¼ 1=2 distorted diamond chain is desired strongly from the experimental point of view.Recently, Kikuchi et al. proposed that Cu 3 (CO 3 ) 2 (OH) 2 might be the first model substance for the S ¼ 1=2 diamond chain. 7) Cu 3 (CO 3 ) 2 (OH) 2 is a well-known natural mineral azurite, which has a dark blue color, and it often contains the natural mineral malachite Cu 2 (OH) 2 (CO 3 ), which has a light green color. However, little was known about the magnetic properties of Cu 3 (CO 3 ) 2 (OH) 2 previously, except for the antiferromagnetic order at T N ¼ 1:9 K from the NMR and magnetic susceptibility measurements 8,9) in the restricted low-temperature region between 1.55...

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“…High-field ESR measurement of Ni(333-tet)(N 3 )(C1O4) has been performed with a backward wave oscillator (BWO) as the light source and pulsed magnetic field up to 16 T. The temperature is varied from 4.2 to 265 K. The details of our high-field ESR systems in Kobe University can be found in [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Submillimeter-wave ESR measurements of low-dimensional quantum spin systems

et al. 2000

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Temperature-dependent electron spin resonance (ESR) measurements of two low-dimensional quantum spin systems, the S = 1/2 spin-ladder system Cu,(1,4-diazacycloheptane),CI 4 (Cu,(C,H 1 ,N 2)2Cl4 ) and the gapless S = I bond-alternating one-dimensional antiferromagnet trans-Ni(333-tet)(N 3 )(CIO4), have been performed. X-band electron spin resonance (ESR) measurements of single-crystal Cu,(C5 H 12 N 2 ) 2 Cl4 show the increase of linewidth and anisotropic g-shifts below 8 K similar to those known for one-dimensional antiferromagnet. On the other hand, Ni(333-tet)(N 3)(C10 4) has broad linewidth and ESR has been observed for the first time by our high-field ESR. Its linewidth increases as the temperature is decreased, while the g-shift seems to be isotropic and the g-value decreases as the temperature is decreased. This g-shift can be connected to the quantum fluctuation of the system.

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Cited by 66 publications

References 23 publications

Magnetic field dependence of the neutron spin resonance inCeB6

Magnetic field dependence of the neutron spin resonance inCeB6

High Field ESR Study of theS=1/2 Diamond-Chain Substance Cu₃(CO₃)₂(OH)₂up to the Magnetization Plateau Region

Submillimeter-wave ESR measurements of low-dimensional quantum spin systems

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Untitled

Cited by 66 publications

References 23 publications

Magnetic field dependence of the neutron spin resonance inCeB6

Magnetic field dependence of the neutron spin resonance inCeB6

High Field ESR Study of theS=1/2 Diamond-Chain Substance Cu3(CO3)2(OH)2up to the Magnetization Plateau Region

Submillimeter-wave ESR measurements of low-dimensional quantum spin systems

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High Field ESR Study of theS=1/2 Diamond-Chain Substance Cu₃(CO₃)₂(OH)₂up to the Magnetization Plateau Region