Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2

H. K. Yoshida; S. E. Dissanayake; A. D. Christianson; C. R. Dela Cruz; Y. Q. Cheng; S. Okamoto; K. Yamaura; M. Isobe; M. Matsuda

doi:10.1103/PhysRevB.102.024445

Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2

H. K. Yoshida, S. E. Dissanayake, A. D. Christianson, C. R. Dela Cruz, Y. Q. Cheng, S. Okamoto, K. Yamaura, M. Isobe, M. Matsuda

Research output: Contribution to journal › Article › peer-review

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Abstract

In Ag2CoO2, Co forms triangular lattice layers, which are separated by the metallic (Ag2) block. The magnetic susceptibility and heat capacity measurements show that this material exhibits an antiferromagnetic transition at TN=17.5 K and the Weiss temperature (TΘ) and the effective moment are -274 K and 1.62μB, respectively, indicating that the Co ion carries spin (S) 1/2 and has a strongly frustrated state with TΘ/TN=15.7. A density functional theory calculation confirmed that the valence state of the Co ions is 2+ and the low-spin state with S=1/2 is realized at reduced on-site Coulomb interaction on Co. We performed elastic and inelastic neutron scattering experiments in a powder sample of Ag2CoO2. Although no noticeable magnetic Bragg peaks were observed below TN, distinct magnetic excitations were observed in the inelastic neutron scattering experiments. The excitations are consistent with those expected for the S=1/2 Heisenberg triangular lattice antiferromagnet. These results suggest that the ordered moment is reduced due to the quantum effect, which explains the absence of the magnetic Bragg peaks. Our results thus suggest that Ag2CoO2 is a good candidate to realize a quantum Heisenberg triangular lattice antiferromagnet.

Original language	English
Article number	024445
Journal	Physical Review B
Volume	102
Issue number	2
DOIs	https://doi.org/10.1103/PhysRevB.102.024445
State	Published - Jul 1 2020

Funding

This research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, which are DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory. A.D.C. and S.O. were supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. During the early stages of this project A.D.C. was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Scientific User Facilities Division. This work was partly supported by JSPS KAKENHI Grants No. 15K17686, No. 18K03529, and No. 20H05276, MEXT, Japan.

Funders	Funder number
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Division of Materials Sciences and Engineering
Japan Society for the Promotion of Science	20H05276, 18K03529, 15K17686
Ministry of Education, Culture, Sports, Science and Technology

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10.1103/PhysRevB.102.024445

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title = "Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2",

abstract = "In Ag2CoO2, Co forms triangular lattice layers, which are separated by the metallic (Ag2) block. The magnetic susceptibility and heat capacity measurements show that this material exhibits an antiferromagnetic transition at TN=17.5 K and the Weiss temperature (TΘ) and the effective moment are -274 K and 1.62μB, respectively, indicating that the Co ion carries spin (S) 1/2 and has a strongly frustrated state with TΘ/TN=15.7. A density functional theory calculation confirmed that the valence state of the Co ions is 2+ and the low-spin state with S=1/2 is realized at reduced on-site Coulomb interaction on Co. We performed elastic and inelastic neutron scattering experiments in a powder sample of Ag2CoO2. Although no noticeable magnetic Bragg peaks were observed below TN, distinct magnetic excitations were observed in the inelastic neutron scattering experiments. The excitations are consistent with those expected for the S=1/2 Heisenberg triangular lattice antiferromagnet. These results suggest that the ordered moment is reduced due to the quantum effect, which explains the absence of the magnetic Bragg peaks. Our results thus suggest that Ag2CoO2 is a good candidate to realize a quantum Heisenberg triangular lattice antiferromagnet.",

author = "Yoshida, {H. K.} and Dissanayake, {S. E.} and Christianson, {A. D.} and {Dela Cruz}, {C. R.} and Cheng, {Y. Q.} and S. Okamoto and K. Yamaura and M. Isobe and M. Matsuda",

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doi = "10.1103/PhysRevB.102.024445",

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T1 - Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2

AU - Yoshida, H. K.

AU - Dissanayake, S. E.

AU - Christianson, A. D.

AU - Dela Cruz, C. R.

AU - Cheng, Y. Q.

AU - Okamoto, S.

AU - Yamaura, K.

AU - Isobe, M.

AU - Matsuda, M.

PY - 2020/7/1

Y1 - 2020/7/1

N2 - In Ag2CoO2, Co forms triangular lattice layers, which are separated by the metallic (Ag2) block. The magnetic susceptibility and heat capacity measurements show that this material exhibits an antiferromagnetic transition at TN=17.5 K and the Weiss temperature (TΘ) and the effective moment are -274 K and 1.62μB, respectively, indicating that the Co ion carries spin (S) 1/2 and has a strongly frustrated state with TΘ/TN=15.7. A density functional theory calculation confirmed that the valence state of the Co ions is 2+ and the low-spin state with S=1/2 is realized at reduced on-site Coulomb interaction on Co. We performed elastic and inelastic neutron scattering experiments in a powder sample of Ag2CoO2. Although no noticeable magnetic Bragg peaks were observed below TN, distinct magnetic excitations were observed in the inelastic neutron scattering experiments. The excitations are consistent with those expected for the S=1/2 Heisenberg triangular lattice antiferromagnet. These results suggest that the ordered moment is reduced due to the quantum effect, which explains the absence of the magnetic Bragg peaks. Our results thus suggest that Ag2CoO2 is a good candidate to realize a quantum Heisenberg triangular lattice antiferromagnet.

AB - In Ag2CoO2, Co forms triangular lattice layers, which are separated by the metallic (Ag2) block. The magnetic susceptibility and heat capacity measurements show that this material exhibits an antiferromagnetic transition at TN=17.5 K and the Weiss temperature (TΘ) and the effective moment are -274 K and 1.62μB, respectively, indicating that the Co ion carries spin (S) 1/2 and has a strongly frustrated state with TΘ/TN=15.7. A density functional theory calculation confirmed that the valence state of the Co ions is 2+ and the low-spin state with S=1/2 is realized at reduced on-site Coulomb interaction on Co. We performed elastic and inelastic neutron scattering experiments in a powder sample of Ag2CoO2. Although no noticeable magnetic Bragg peaks were observed below TN, distinct magnetic excitations were observed in the inelastic neutron scattering experiments. The excitations are consistent with those expected for the S=1/2 Heisenberg triangular lattice antiferromagnet. These results suggest that the ordered moment is reduced due to the quantum effect, which explains the absence of the magnetic Bragg peaks. Our results thus suggest that Ag2CoO2 is a good candidate to realize a quantum Heisenberg triangular lattice antiferromagnet.

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Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2

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