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Title: Magnetic ground state of the two isostructual polymeric quantum magnets [Cu(HF2)(pyrazine)2]SbF6 and [Co(HF2)(pyrazine)2]SbF6 investigated with neutron powder diffraction

The magnetic ground state of two isostructural coordination polymers, (i) the quasi-two-dimensional S=1/2 square-lattice antiferromagnet [Cu(HF2)(pyrazine)2]SbF6 and (ii) a related compound [Co(HF2)(pyrazine)2]SbF6, was examined with neutron powder diffraction measurements. We find that the ordered moments of the Heisenberg S=1/2 Cu(II) ions in [Cu(HF2)(pyrazine)2]SbF6 are 0.6(1)μb, while the ordered moments for the Co(II) ions in [Co(HF2)(pyrazine)2]SbF6 are 3.02(6)μb. For Cu(II), this reduced moment indicates the presence of quantum fluctuations below the ordering temperature. We also show from heat capacity and electron spin resonance measurements that due to the crystal electric field splitting of the S=3/2 Co(II) ions in [Co(HF2)(pyrazine)2]SbF6, this isostructual polymer also behaves as an effective spin-half magnet at low temperatures. Furthermore, the Co moments in [Co(HF2)(pyrazine)2]SbF6 show strong easy-axis anisotropy, neutron diffraction data, which do not support the presence of quantum fluctuations in the ground state, and heat capacity data, which are consistent with 2D or close to 3D spatial exchange anisotropy.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [2] ;  [2] ;  [4] ;  [5] ;  [5] ;  [6] ;  [7] ;  [7] ;  [7] ;  [7] ;  [7] ;  [7]
  1. Univ. of Warwick, Coventry (United Kingdom). Dept. of Physics
  2. Univ. of Oxford (United Kingdom). Dept. of Physics
  3. Univ. of Oxford (United Kingdom). Dept. of Materials
  4. Durham Univ. (United Kingdom). ISIS Pulsed Neutron and Muon Facility
  5. ISIS Pulsed Neutron and Muon Facility, Oxfordshire (United Kingdom)
  6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab.
  7. Eastern Washington Univ., Cheney, WA (United States). Dept. of Chemistry and Biochemistry
Publication Date:
OSTI Identifier:
1334127
Report Number(s):
LA-UR--15-27163
Journal ID: ISSN 1098-0121; PRBMDO
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 92; Journal Issue: 13; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY High Magnetic Field Science