skip to main content

DOE PAGESDOE PAGES

This content will become publicly available on November 17, 2017

Title: Revisiting the ground state of CoAl2O4 : Comparison to the conventional antiferromagnet MnAl2O4

The A-site spinel material CoAl2O4 is a physical realization of the frustrated diamond-lattice antiferromagnet, a model in which unique incommensurate or “spin-spiral-liquid” ground states are predicted. Our previous single-crystal neutron scattering study instead classified it as a “kinetically inhibited” antiferromagnet, where the long-ranged correlations of a collinear Néel ground state are blocked by the freezing of domain-wall motion below a first-order phase transition at T*=6.5 K. This study provides new data sets from a number of experiments, which support and expand this work in several important ways. We show that the phenomenology leading to the kinetically inhibited order is unaffected by sample measured and instrument resolution, while new low-temperature measurements reveal spin correlations are unchanging between T=2 K and 250 mK, consistent with a frozen state. Polarized diffuse neutron measurements show several interesting magnetic features, which can be entirely explained by the existence of short-ranged Néel order. Finally, and crucially, this paper presents some neutron scattering studies of single crystalline MnAl2O4, which acts as an unfrustrated analog to CoAl2O4 and shows all the hallmarks of a classical antiferromagnet with a continuous phase transition to Néel order at TN=39 K. Direct comparison between the two compounds indicates that CoAl2O4 is unique,more » not in the nature of high-temperature diffuse correlations, but rather in the nature of the frozen state below T*. Finally, the higher level of cation inversion in the MnAl2O4 sample indicates that this behavior is primarily an effect of greater next-nearest-neighbor exchange.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [2] ;  [7] ;  [8] ;  [9] ;  [10]
  1. Univ. of Illinois, Urbana, IL (United States). Dept. of Physics; Seitz Materials Research Lab.; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
  3. Forschungszentrum Julich GmbH, Garching (Germany). Julich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ)
  4. Forschungszentrum Julich GmbH (Germany). Julich Centre for Neutron Science (JCNS)
  5. Forschungszentrum Julich GmbH, Garching (Germany). Julich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ); Helmholtz-Zentrum Berlin for Materials and Energy, Berlin (Germany)
  6. Helmholtz-Zentrum Berlin for Materials and Energy, Berlin (Germany); Forschungsneutronenquell Heinz Meier-Leibnitz (FRM-II), Garching (Germany)
  7. Ames Lab. and Iowa State Univ., Ames, IA (United States). Division of Materials Science and Engineering
  8. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; National High Magnetic Field Lab., Tallahassee, FL (United States)
  9. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  10. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division; Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center
Publication Date:
OSTI Identifier:
1335348
Grant/Contract Number:
AC05-00OR22725; DMR-1455264-CAR; NSF-DMR-1157490
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 18; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Illinois, Urbana, IL (United States); Univ. of Tennessee, Knoxville, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF) (United States)
Contributing Orgs:
Forschungszentrum Julich GmbH, Garching (Germany); Forschungszentrum Julich GmbH (Germany); Helmholtz-Zentrum Berlin for Materials and Energy, Berlin (Germany); Forschungsneutronenquell Heinz Meier-Leibnitz (FRM-II), Garching (Germany); Ames Lab. and Iowa State Univ., Ames, IA (United States); National High Magnetic Field Lab., Tallahassee, FL (United States)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY inelastic neutron scattering; spinel; antiferromagnet