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Title: Effects of chemical pressure on the magnetic ground states of the osmate double perovskites SrCaCoOs 6 and Ca 2CoOsO 6

The magnetic ground state in the double perovskite system Sr 2-xCa xCoOsO 6 changes from an antiferromagnet (x=0), to a spin glass (x=1), to a ferrimagnet (x=2) as the Ca content increases. Moreover, this crossover is driven by chemical pressure effects that control the relative strength of magnetic exchange interactions. The synthesis, crystal structure, and magnetism of SrCaCoOsO 6 and Ca 2CoOsO 6 are investigated and compared with Sr 2CoOsO 6. Both compounds adopt a monoclinic crystal structure with rock-salt ordering of Co 2+ and Os 6+ and a -a -b + octahedral tilting, but the average Co–O–Os bond angle evolves from 158.0(3) in SrCaCoOsO 6 to 150.54(9)° in Ca 2CoOsO 6 as the smaller Ca 2+ ion replaces Sr 2+. And while this change may seem minor, it has a profound effect on the magnetism, changing the magnetic ground state from antiferromagnetic in Sr 2CoOsO 6 (TN1=108K, T N2=70K), to a spin glass in SrCaCoOsO 6 (T f1=32K, T f2=13K), to ferrimagnetic in Ca 2CoOsO 6 (T C=145K). Finally, in the first two compounds the observation of two transitions is consistent with weak coupling between the Co and Os sublattices.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [1]
  1. The Ohio State Univ., Columbus, OH (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 92; Journal Issue: 9; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
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
OSTI Identifier:
1265814
Alternate Identifier(s):
OSTI ID: 1222364