Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron Antiferromagnet Ca_(1-x)Sr_xCo_(2-y)As_2

摘要

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 Ca1-xSrxCo2-yAs2 with the body-centered tetragonal ThCr2Si2 structure is confirmed. Our major finding is an anomalous magnetic behavior in the crossover region 0.2 less than or similar to x less than or similar to 0.3 between these two phases. In this region the magnetic susceptibility vs temperature chi(ab)(T) measured with magnetic fields H applied in the ab plane exhibit typical AFM behaviors with cusps at the Neel temperatures of similar to 65 K, whereas chi(c)(T) and the low-temperature isothermal magnetization M-c (H) with H aligned along the c axis exhibit extremely soft ferromagneticlike behaviors.