Magnetic Properties of La$_{0.7}$Sr$_{0.3}$Mn$_{1-x}$Ni$_x$O$_3$ Perovskites

Using a SQUID magnetometer, we have studied the magnetic properties of La$_{0.7}$Sr$_{0.3}$Mn$_{1-x}$Ni$_{x}$O$_{3}$ ($x=0.05$, 0.10, 0.20 and 0.30) perovskites. Both temperature dependent and field dependent magnetic measurements show that the Curie temperature decreases as a function of doping, ranging from 380K in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ to 300K in La$_{0.7}$Sr$_{0.3}$Mn$_{0.7}$Ni$_{0.3}$O$_{3}$. Both magnetic measurements and neutron-diffraction refinements indicate long-range magnetic ordering in samples at low temperature. Transition phases from paramagnetic to ferromagnetic to antiferromagnetic ordering in samples at room temperature.