Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron Antiferromagnet Ca1-xSrxCo2-yAs2

We report the inference of Ying et al. [Europhys. Lett. 104, 67005 (2013)] of a composition-induced change from c-axis ordered-moment alignment in a collinear A-type antiferromagnetic (AFM) structure at small x to ab-plane alignment in an unknown AFM structure at larger x in Ca_1-xSr_xCo_2-yAs₂ with the body-centered tetragonal ThCr₂Si₂ structure is confirmed. Our major finding is an anomalous magnetic behavior in the crossover region 0.2 ≲ x ≲ 0.3 between these two phases. Also, in this region the magnetic susceptibility vs temperature χ_ab(T) measured with magnetic fields H applied in the ab plane exhibit typical AFM behaviors with cusps at the Néel temperatures of ~ 65 K, whereas χ_c(T) and the low-temperature isothermal magnetization M_c(H) with H aligned along the c axis exhibit extremely soft ferromagneticlike behaviors.