Itinerant G-type antiferromagnet SrCr2 As2 studied by magnetization, heat capacity, electrical resistivity, and NMR measurements

The physical properties of itinerant antiferromagnetic (AFM) SrCr2As2 with body-centered tetragonal ThCr2Si2 structure were investigated in single crystalline and polycrystalline forms by electrical resistivity ρ, heat capacity Cp, magnetic susceptibility χ versus temperature T, and magnetization M versus applied magnetic field H isotherm measurements as well as As75 and Cr53 nuclear magnetic resonance (NMR) measurements in the wide temperature range T = 1.6-900 K. From the χ(T) and As75 NMR measurements, the G-type AFM state below TN = 615(15) K has been determined, consistent with the previous neutron-diffraction measurements. Direct evidence of magnetic ordering of the Cr spins was shown by the observation of the Cr53 NMR spectrum under H = 0. From the χ(T) measurements on single-crystal SrCr2As2 under the two different magnetic field directions H||ab and H||c in the AFM state, the Cr ordered moments are shown to align along the c axis in the G-type AFM state. The metallic state is directly evidenced by the ρ, Cp, and NMR measurements, and the density of states at the Fermi energy D(EF) in the AFM state is estimated to be 7.53 states/eV f.u. for both spin directions which is almost twice the bare D(EF) estimated from first-principles calculations, suggesting an enhancement of the conduction-carrier mass by a factor of two in the AFM state. The D(EF) is found to be nearly constant below at least 100 K and is independent of H. The ρ(T) is found to show T-linear behavior above TN and exhibits positive curvature below TN where significant loss of spin-disorder scattering upon magnetic ordering is observed. The resistivity anisotropy of the compound remains moderate ρc/ρa∼9 through most of the magnetically ordered phase but shows a rapid increase below 50 K.