Metallic behavior induced by potassium doping of the trigonal antiferromagnetic insulator EuMn2As2

Article

关键词: HIGH-TEMPERATURE SUPERCONDUCTIVITY;    ELECTRONIC-PROPERTIES;    CAAL2SI2 STRUCTURE;    AB2X2 COMPOUNDS;    MAGNETIC-STRUCTURE;    CRYSTAL-STRUCTURE;    IRON PNICTIDES;    YBMN2SB2;    STATE;    ORDER;   

DOI  :  10.1103/PhysRevB.94.014431

来源: SCIE

【 摘 要 】

We report magnetic susceptibility chi, isothermal magnetization M, heat capacity C-p, and electrical resistivity rho measurements on undoped EuMn2As2 and K-doped Eu0.96K0.04Mn2As2 and Eu0.93K0.07Mn2As2 single crystals with the trigonal CaAl2Si2-type structure as a function of temperature T and magnetic field H. EuMn2As2 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 chi(T) data with a likely spin-reorientation transition at T-N2 = 5.0 K. TheMn(+) 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 chi(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 Eu0.96K0.04Mn2As2 is sufficient to induce a metallic ground state. Evidence is found for a difference in the AFM structure of the Eu moments in the metallic crystals from that of undoped EuMn2As2 versus both T and H. For metallic Eu0.96K0.04Mn2As2 and Eu0.93K0.07Mn2As2, an anomalous S-shape T dependence of rho related to the Mn magnetism is found. Upon cooling from 200 K, rho exhibits a strong negative curvature, reaches maximum positive slope at the Mn T-N approximate to 150 K, and then continues to decrease but more slowly below T-N. 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 rho that is only observed upon cooling below T-N of an antiferromagnet.

【 授权许可】

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