Metamagnetic transition in Ca1-xSrxCo2As2(x=0 and 0.1) single crystals

We report the magnetic and transport measurements of CaCo2As2 and Ca0.9Sr0.1Co2As2 single crystals. An antiferromagnetic transition was observed at about 70 K and 90 K for CaCo2As2 and Ca0.9Sr0.1Co2As2, respectively. Magnetic and magnetoresistance measurements reveal a metamagnetic transition from an antiferromagnetic state to a ferromagnetic state with a critical field of 3.5 and 1.5 T for these two samples, respectively along the c axis at low temperature. For the field applied along the ab plane, spins can be fully polarized above a field of 4.5 T for Ca0.9Sr0.1Co2As2. While for CaCo2As2, spins cannot be fully polarized up to 7 T. We propose the cobalt moments of these two materials should be ordered ferromagnetically within the ab plane but antiferromagnetically along the c axis (A-type antiferromagnetic).