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Title: Strong magnetic correlations to 900 K in single crystals of the trigonal antiferromagnetic insulators SrMn2As2 and CaMn2As2

Crystallographic, electronic transport, thermal, and magnetic properties are reported for SrMn2As2 and CaMn2As2 single crystals grown using Sn flux. Rietveld refinements of powder x-ray diffraction data show that the two compounds are isostructural and crystallize in the trigonal CaAl2Si2-type structure (space group $$P\bar{3}$$ m1), in agreement with the literature. Electrical resistivity ρ versus temperature T measurements demonstrate insulating ground states for both compounds with activation energies of 85 meV for SrMn2As2 and 61 meV for CaMn2As2. In a local-moment picture, the Mn+2 3d5 ions are expected to have high-spin S=5/2 with spectroscopic splitting factor g≈2. Magnetic susceptibility χ and heat capacity Cp measurements versus T reveal antiferromagnetic (AFM) transitions at TN=120(2) K and 62(3) K for SrMn2As2 and CaMn2As2, respectively. The anisotropic χ(T≤TN) data indicate that the hexagonal c axis is the hard axis and hence that the ordered Mn moments are aligned in the ab plane. Finally, the χ(T) data for both compounds and the Cp(T) for SrMn2As2 show strong dynamic short-range AFM correlations from TN up to at least 900 K, likely associated with quasi-two-dimensional connectivity of strong AFM exchange interactions between the Mn spins within the corrugated honeycomb Mn layers parallel to the ab plane.
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
Publication Date:
OSTI Identifier:
1326842
Report Number(s):
IS-J-9072
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 9; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY