Submillimetre-wave electron spin-resonance measurements for single-crystal

Kimura, Shojiro; Ohta, H.; Mitsudo, S.; Motokawa, M.; Jang, Wen-Jye; Hasegawa, Masashi; Takei, Hiroyuki

doi:10.1088/0953-8984/8/29/019

Cited by 14 publications

(7 citation statements)

References 26 publications

(61 reference statements)

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“…However, the slope of the magnetization above 13 T for B//c does not coincide with the slope of that for B⊥c, while they usually coincide for the typical S=1/2 two sublattice antiferromagnet because the single ion type anisotropy is not expected in the S=1/2 system. However, such a deviation in the magnetization was also observed in Y 2 Cu 2 O 5 [4], and it was interpreted by the consideration of the multi-sublattice model [5]. Moreover, the magnetization result of dioptase seems to coincide with the fact that our AFMR results at 1.8 K start to deviate from the AFMR modes calculated by the two sublattice molecular field theory [6,7] above B c for B//c [2].…”

Section: Methodssupporting

confidence: 70%

Magnetic susceptibility measurement under high pressure and magnetization measurement of S = 1/2 dioptase lattice antiferromagnet

Ohta

Fujisawa

Souda

et al. 2009

J. Phys.: Conf. Ser.

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Abstract. Natural mineral Dioptase (Cu6Si6O18 · 6H2O) is an S=1/2 antiferromagnet with a unique spin network which consists of helical chains along the c axis connected by inter chain exchange interactions. In order to study the ground state of dioptase, we have performed the magnetization measurement for B//c (easy axis) at 1.5 K and have found the spin-flop transition at 13 T. Moreover, the pressure effect of the magnetic susceptibility is investigated up to 1.78 GPa using the SQUID magnetometer where TN increased while the broad maximum reflecting the low dimensionality of the system decreased by pressure. The results will be discussed in connection with our previous antiferromagnetic resonance (AFMR) measurement results and the phase diagram obtained by Gros et al. IntroductionNatural mineral Dioptase (Cu 6 Si 6 O 18 · 6H 2 O) is a unique S=1/2 antiferromagnet where Cu 2+ ions form the antiferromagnetic helical chain along the c-axis (the exchange interaction J 2 = J(1 − δ) and the chains are antiferromagnetically connected (the exchange interaction. This unique spin network is called the dioptase lattice and the phase diagram of its ground state is obtained by the Quantum Monte Carlo calculation [1]. As shown in Fig. 1 the calculation suggests that the quantum critical point at δ =0.3 is expected in between the antiferromagnetic order phase (δ <0.3) and the spin gap phase (δ >0.3) [1]. However, the magnetic susceptibility of dioptase shows a broad maximum around 45 K and the antiferromagnetic order is observed at T N =15.5 K. Its analysis by the Quantum Monte Carlo calculation suggest δ =0.1, J=56.6 K, g=2.09 or δ =-0.1, J=53.4 K, g=2.10 for dioptase [1]. Moreover, our previous high field ESR result at 1.8 K clearly shows the existence of antiferromagnetic order below T N by the observation of AFMR, and the existence of the spin-flop

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Section: Methodssupporting

confidence: 70%

Magnetic susceptibility measurement under high pressure and magnetization measurement of S = 1/2 dioptase lattice antiferromagnet

Ohta

Fujisawa

Souda

et al. 2009

J. Phys.: Conf. Ser.

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“…The calculated values of J 0 /k and J 1 /k were 100 K and 82 K, respectively. On the other hand, analysis of the antiferromagnetic modes below T N in submillimetre-wave ESR technique gave for the same exchange couplings the values 340 K and -0.33 K [12]. As for the value of the sum of interchain interactions zJ′ (where z is the number of copper magnetic neighbors) it ranges from -1.…”

Section: Resultsmentioning

confidence: 89%

“…To explain the appearance of metamagnetic transitions in the antiferromagnetic phase of the R 2 Cu 2 O 5 compounds a model has been proposed assuming pairing of two neighbouring Cu 2+ spins in the copper chain along the a-axis [11][12][13]. This way chains of copper dimers S = 1 is formed, which are aligned ferromagnetically.…”

Section: Originalmentioning

confidence: 99%

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Competing magnetic interactions in (Dy_0.375Y_0.625)₂Cu₂O₅ solid solution studied by EPR

Typek

2007

Physica Status Solidi (b)

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structure has been found in the EPR spectrum and the values of appropriate exchange constants connected with a hierarchy of exchange interactions has been calculated. At about 40 K a dimensional crossover from 2D to 3D behaviour has been observed in the temperature dependence of the product of the EPR integrated intensity and temperature. At high temperatures (T > 200 K) the EPR spectrum is suggestive of the presence of defect centres consisting of antferromagnetically coupled copper spins, forming dimers with the S = 0 ground state.

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“…This is because the density of state should be large there. For instance, this fact is clearly indicated by the comparison of the powder and single crystal measurements of Y 2 Cu 2 O 5 [16,17]. Therefore, an broad rectangular shaped absorption, which is observed at around 2 T below 140 GHz, should correspond to two absorption lines.…”

Section: +mentioning

confidence: 89%

High frequency ESR measurements of high pressure phase SiCo ₂ O ₄

Zhang

Okubo

Ohta

et al. 2006

Phys. Status Solidi (c)

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New Co spinel compound SiCo 2 O 4 have been synthesized by using the high-pressure synthesis technique. High frequency ESR measurements of powder samples of SiCo 2 O 4 have been performed by using the pulsed magnetic field up to 16 T in the frequency range from 60 GHz to 540 GHz. From the frequencyfield diagram at 1.8 K two critcal field resonances are observed at 1.7 T, which correspond to the field of the metamagnetic transition and 2.3 T. The g-values are estimated to be 6.7 and 4.5 from the ESR mode in the field induced ferromagnet phase.

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Submillimetre-wave electron spin-resonance measurements for single-crystal

Cited by 14 publications

References 26 publications

Magnetic susceptibility measurement under high pressure and magnetization measurement of S = 1/2 dioptase lattice antiferromagnet

Magnetic susceptibility measurement under high pressure and magnetization measurement of S = 1/2 dioptase lattice antiferromagnet

Competing magnetic interactions in (Dy_0.375Y_0.625)₂Cu₂O₅ solid solution studied by EPR

High frequency ESR measurements of high pressure phase SiCo ₂ O ₄

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Submillimetre-wave electron spin-resonance measurements for single-crystal

Cited by 14 publications

References 26 publications

Magnetic susceptibility measurement under high pressure and magnetization measurement of S = 1/2 dioptase lattice antiferromagnet

Magnetic susceptibility measurement under high pressure and magnetization measurement of S = 1/2 dioptase lattice antiferromagnet

Competing magnetic interactions in (Dy0.375Y0.625)2Cu2O5 solid solution studied by EPR

High frequency ESR measurements of high pressure phase SiCo 2 O 4

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Product

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About

Competing magnetic interactions in (Dy_0.375Y_0.625)₂Cu₂O₅ solid solution studied by EPR

High frequency ESR measurements of high pressure phase SiCo ₂ O ₄