Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron Antiferromagnet Ca_{1-x}Sr_{x}Co_{2-y}As_{2}.

The inference of Ying et al. [Europhys. Lett. 104, 67005 (2013)EULEEJ0295-507510.1209/0295-5075/104/67005] 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-x}Sr_{x}Co_{2-y}As_{2} with the body-centered tetragonal ThCr_{2}Si_{2} structure is confirmed. Our major finding is an anomalous magnetic behavior in the crossover region 0.2≲x≲0.3 between these two phases. 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.