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Title: Metallic behavior induced by potassium doping of the trigonal antiferromagnetic insulator EuMn 2 As 2

Here, we report magnetic susceptibility χ, isothermal magnetization M, heat capacity C p, and electrical resistivity ρ measurements on undoped EuMn 2As 2 and K-doped Eu 0.96K 0.04Mn 2As 2 and Eu 0.93K 0.07Mn 2As 2 single crystals with the trigonal CaAl 2Si 2-type structure as a function of temperature T and magnetic field H. EuMn 2As 2 has an insulating ground state with an activation energy of 52 meV and exhibits antiferromagnetic (AFM) ordering of the Eu +2 spins S=7/2 at T N1=15 K from C p(T) and χ(T) data with a likely spin-reorientation transition at T N2=5.0 K. The Mn +2 3d 5 spins-5/2 exhibit AFM ordering at T N=142 K from all three types of measurements. The M(H) isotherm and χ(T) data indicate that the Eu AFM structure is both noncollinear and noncoplanar. The AFM structure of the Mn spins is also unclear. A 4% substitution of K for Eu in Eu 0.96K 0.04Mn 2As 2 is sufficient to induce a metallic ground state. We found evidence for a difference in the AFM structure of the Eu moments in the metallic crystals from that of undoped EuMn 2As 2 versus both T and H. For metallic Eumore » 0.96K 0.04Mn 2As 2 and Eu 0.93K 0.07Mn 2As 2, an anomalous S-shape T dependence of ρ related to the Mn magnetism is found. Upon cooling from 200 K, ρ exhibits a strong negative curvature, reaches maximum positive slope at the Mn T N≈150 K, and then continues to decrease but more slowly below T N. Finally, this suggests that dynamic short-range AFM order of the Mn spins above the Mn T N strongly suppresses the resistivity, contrary to the conventional decrease of ρ that is only observed upon cooling below T N of an antiferromagnet.« less
 [1] ;  [2]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy; Helmholtz-Zentrum Berlin for Materials and Energy, Berlin (Germany)
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
Publication Date:
Report Number(s):
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 1; Journal ID: ISSN 2469-9950
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
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1268449