Magnetic properties of the spin-ladder material Na2Co2(C2O4)3(H2O)2Na2Co2(C2O4)3(H2O)2 doped with Zn

Effects of Zn impurities on a spin-ladder material Na2Co2(C2O4)3(H2O)2Na2Co2(C2O4)3(H2O)2 are reported. We measured the magnetic susceptibility, χχ on a single crystal and find that χχ at a high field shows a broad peak at about 20 K and a Curie-tail at low temperatures. We interpret the low temperature Curie-tail as due to an induced moment around Zn impurities. At a low field, we find a spin-glass behavior evidenced by a difference in χχ for field cooled and zero field cooled measurements. We present a possible mechanism for the appearance of this spin glass.