Physical properties of metallic antiferromagnetic CaCo1.86As2 single crystals

X-ray powder diffraction (XRD), magnetic susceptibility., isothermal magnetization M, heat capacity Cp, and in-plane electrical resistivity. measurements as a function of temperature T and magnetic field H are presented for CaCo1.86As2 single crystals. The electronic structure is probed by angle-resolved photoemission spectroscopy (ARPES) measurements of CaCo1.86As2 and by full-potential linearized augmented-plane-wave calculations for the supercell CaCo1.86As2 (CaCo1.86As2). OurXRDcrystal structure refinement is consistent with the previous combined refinement of x-ray and neutron powder diffraction data showing a collapsed-tetragonal ThCr2Si2-type structure with 7(1)% vacancies on the Co sites corresponding to the composition CaCo1.86As2 [ D. G. Quirinale et al., Phys. Rev. B 88, 174420 (2013)]. The anisotropic.(T) data are consistent with the magnetic neutron diffraction data of Quirianale et al. that demonstrate the presence of A-type collinear antiferromagnetic order below the N ' eel temperature TN = 52(1) K with the easy axis being the tetragonal c axis. However, no clear evidence from the.(T) and Cp(T) data for a magnetic transition at TN is observed. A metallic ground state is demonstrated from the band calculations and the.(T), C-p(T), and ARPES data, and spin-polarized calculations indicate a competition between the A-type AFM and FM ground states. The C-p(T) data exhibit a large Sommerfield electronic coefficient reflecting a large density of states at the Fermi energy D(EF) that is enhanced compared with the band structure calculation where the bare D(EF) arises from Co 3d bands. At 1.8 K, theM(H) data for Hc exhibit a well-defined first-order spin-flop transition at an applied field of 3.5 T. The small ordered moment of 0.3 B/Co obtained from the M(H) data at low T, the large exchange enhancement of. and the lack of a self-consistent interpretation of the.(T) and M(H, T) data in terms of a local moment Heisenberg model together indicate that the magnetism of CaCo1.86As2 is itinerant.