The effect of transition element doping on the electronic and magnetic properties of La1.4Sr1.6Mn2O7

The effect of transition element (TE=Cr, Fe, Co, Ni, Cu, Zn) doping on the electronic transport and magnetic properties in the bilayer manganite La_1.4Sr_1.6Mn₂O₇ is studied for the same dopant concentration fixed at 2%. Doping does not cause change in structure but different behavior in magnetic and transport properties. Except for Cr, all the other dopings significantly shift the magnetic transition temperature (T_C) to a lower temperature. Associated with such a decrease, the insulator-metal transition temperature (T_IM) decreases and the peak resistivity (ρ_p) at T_IM increases. Cr doping enhances T_C and T_IM as well as decreases ρ_p. Fe doping apparently has a stronger effect than Co and Ni doping. It is also indicated that Cu doping causes an anomalously large increase in ρ_p. These behaviors are compared with those observed in other bilayer manganites such as La_1.2Sr_1.8Mn₂O₇ as well as in La_0.7Ca_0.3Mn_1−xTE_xO₃.