Cr doping in the La1.2Sr1.8Mn2O7 system

The effect of doping Cr in the Mn site of the La(1.2)Srl(1.8)Mn(2)O(7) syst em has been studied. Addition of Cr modifies the transport and magnetic pro perties of the parent phase. With increasing Cr, the insulator-metal transi tion observed in the parent phase is suppressed and insulating behaviour is induced. In the range of doping studied (25%), the compositions show ferro magnetic behaviour with the Curie temperature decreasing with increasing Cr . The unit cell volume also shows a decrease. However, the magnetoresistanc e ratio is not significantly affected. We compare these results with an ear lier study of doping Cr in the three-dimensional LaMnO3 structure, where it was seen that the ferromagnetic and magnetoresistance characteristics are sensitive to Cr doping. The results of the present study suggest that the l ayered manganates are more accommodative to doping compared to the three-di mensional perovskites.