Effect of Cr doping in the bilayer manganite La1.4Sr1.6Mn2O7

The effect of Cr doping on magnetic and electrical properties in the bilayer manganites La1.4Sr1.6(Mn1−yCry)2O7 (y=0–0.1) has been investigated. When y≤0.025, Cr doping enhances the three-dimensional magnetic transition temperature TC and the insulator–metal transition temperature TIM as well as decreases the peak resistivity at TIM, and the saturated magnetization decreases slightly. When y≥0.035, TIM decreases gradually accompanied by the increase of peak resistivity, but TC remains nearly constant, and the saturated magnetization decreases heavily. In the whole doping region, the two-dimensional magnetic transition temperature T⁎ monotonously decreases with an increasing of Cr doping level. These results can be explained by considering different magnetic (including ferromagnetic and antiferromagnetic) interactions between Mn ions and Cr ions.

Research highlights
► Cr doping results in a novel change on magnetic and electrical properties.
► For low doping, the magnetic coupling between Cr and Mn ions is ferromagnetic.
► For high doping, the magnetic coupling between Cr and Mn ions is antiferromagnetic.
► High Cr doping results in phase separation.
► Cr doping suppresses the short range two-dimensional ferromagnetic ordering.