Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet

Q Huang; R Rawl; W W Xie; E S Chou; V S Zapf; X X Ding; C Mauws; C R Wiebe; E X Feng; H B Cao; W Tian; J Ma; Y Qiu; N Butch; H D Zhou

doi:10.1088/1361-648X/ac5703

Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet

J Phys Condens Matter. 2022 Mar 10;34(20). doi: 10.1088/1361-648X/ac5703.

Authors

Q Huang¹, R Rawl¹, W W Xie², E S Chou³, V S Zapf⁴, X X Ding⁴, C Mauws⁵, C R Wiebe^{5

6

7}, E X Feng⁸, H B Cao⁸, W Tian⁸, J Ma^{9

10}, Y Qiu¹¹, N Butch¹¹, H D Zhou^{1

3}

Affiliations

¹ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, United States of America.
² Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, United States of America.
³ National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, United States of America.
⁴ National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87545, United States of America.
⁵ Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
⁶ Department of Chemistry, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada.
⁷ Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
⁸ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America.
⁹ Laboratory of Artificial Structures and Quantum Control, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
¹⁰ Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang, People's Republic of China.
¹¹ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States of America.

PMID: 35189602
DOI: 10.1088/1361-648X/ac5703

Abstract

With the motivation to study how non-magnetic ion site disorder affects the quantum magnetism of Ba₃CoSb₂O₉, a spin-1/2 equilateral triangular lattice antiferromagnet, we performed DC and AC susceptibility, specific heat, elastic and inelastic neutron scattering measurements on single crystalline samples of Ba_2.87Sr_0.13CoSb₂O₉with Sr doping on non-magnetic Ba²⁺ion sites. The results show that Ba_2.87Sr_0.13CoSb₂O₉exhibits (i) a two-step magnetic transition at 2.7 K and 3.3 K, respectively; (ii) a possible canted 120 degree spin structure at zero field with reduced ordered moment as 1.24μ_B/Co; (iii) a series of spin state transitions for bothH∥ab-plane andH∥c-axis. ForH∥ab-plane, the magnetization plateau feature related to the up-up-down phase is significantly suppressed; (iv) an inelastic neutron scattering spectrum with only one gapped mode at zero field, which splits to one gapless and one gapped mode at 9 T. All these features are distinctly different from those observed for the parent compound Ba₃CoSb₂O₉, which demonstrates that the non-magnetic ion site disorder (the Sr doping) plays a complex role on the magnetic properties beyond the conventionally expected randomization of the exchange interactions. We propose the additional effects including the enhancement of quantum spin fluctuations and introduction of a possible spatial anisotropy through the local structural distortions.

Keywords: geometrically frustrated magnet; phase transitions; site disorder.