X-ray powder diffraction (XRD), magnetic susceptibility χ, isothermal magnetization M , heat capacity Cp and in-plane electrical resistivity ρ 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 Ca8Co15As16 (CaCo1.88As2). Our XRD crystal 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 χ(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 Néel temperature TN = 52(1) K with the easy axis being the tetragonal c axis. However, no clear evidence from the ρ(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 ρ(T ), Cp(T ) and ARPES data, and spin-polarized calculations indicate a competition between the A-type AFM and FM ground states. The Cp(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 the M (H) data for H c exhibit a well-defined first-order spin-flop transition at an applied field of 3.5 T. The small ordered moment of ≈ 0.3 µB/Co obtained from the M (H) data at low T , the large exchange enhancement of χ and the lack of a self-consistent interpretation of the χ(T ) and M (H, T ) data in terms of a local moment Heisenberg model together indicate that the magnetism of CaCo1.86As2 is itinerant.

Neutron and x-ray diffraction measurements are presented for powders and single crystals of CaCo 2 As 2 . The crystal structure is a collapsed-tetragonal ThCr 2 Si 2 -type structure as previously reported, but with 7(1)% vacancies on the Co sites corresponding to the composition CaCo 1.86(2) As 2 . The thermal expansion coefficients for both the a and c axes are positive from 10 to 300 K. Neutron diffraction measurements on single crystals demonstrate the onset of A-type collinear antiferromagnetic order below the Néel temperature T N = 52(1) K with the ordered moments directed along the tetragonal c axis, aligned ferromagnetically in the ab plane and antiferromagnetically stacked along the c axis.

We report the synthesis, structure, and magnetic and transport properties of a new ternary intermetallic compound PrRhSn3 which crystallizes in LaRuSn3-type cubic structure (space group P m3n). At low applied fields the dc magnetic susceptibility exhibits a sharp anomaly below 6 K with an irreversible behavior in zero field cooled (ZFC) and field cooled (FC) susceptibility below 5.5 K. The ac susceptibility exhibits a frequency dependent anomaly revealing a spin-glass behavior with a freezing temperature, T f = 4.3 K. The observation of spin-glass behavior is further supported by a very slow decay of thermo-remnant magnetization (mean relaxation time τ = 2149 s). However, a small jump at very low field in the isothermal magnetization at 2 K and a weak anomaly in the specific heat near 5.5 K reveal the presence of ferromagnetic clusters. The frequency dependence of the transition temperature T f in the ac susceptibility obeys the Vogel-Fulcher law, ν = ν0exp[−Ea/kB(T f − T0)] with activation energy Ea/kB = 19.1 K. This together with an intermediate value of the parameter δT f = ∆T f /T f ∆(log 10 ν) = 0.086 provide an evidence for the formation of a cluster-glass state in PrRhSn3. Further, we have analyzed the frequency dependence of transition temperature within the framework of critical slowing down, τ = τ0[(T f −TSG)/TSG) −zν ′ ] and found the characteristic time constant τ0 = 2.04 × 10 −10 s and critical exponent zν ′ = 10.9, which also support a cluster spin-glass behavior in this compound. The magnetic contribution of the specific heat reveals a broad Schottky-type anomaly centered around 10 K and the analysis based on the crystal electric field model indicates a singlet ground state. Further, below T f the magnetic part of the specific heat exhibits a T 3/2 temperature dependence. The strong influence of the crystal electric field and a T 3/2 temperature dependence are also seen in the electrical resistivity which reveals a metallic character and a high magnetoresistance. We also obtain a surprisingly large value of Sommerfeld-Wilson ratio RW ≈ 247.