Effect of Ga doping for Mn on the magnetic properties of La_0.67Ca_0.33MnO₃

Abstract

The effect of Ga substitution for Mn in the ferromagnetic manganite La_0.67Ca_0.33MnO₃ has been studied by preparing a series of La_0.67Ca_0.33Mn_1−xGa_xO₃ (x = 0, 0.10, 0.25). Magnetic properties have been investigated by means of macroscopic ac susceptibility and dc magnetization, mesoscopic neutron depolarization, and microscopic neutron-diffraction probes. The substitution of Mn³⁺ by nonmagnetic Ga³⁺ allows one to study the effect of a reduction of the number of lattice sites participating in the itinerant ferromagnetic double exchange interaction, i.e., a dilution of the magnetic Mn sublattice. In contrast to other Mn site substitutions, changes of the electronic band structure by structural effects are small due to similar ionic size of Mn³⁺ and Ga³⁺. Experimental results show that the ferromagnetism at low temperature is suppressed and the system is driven into a randomly canted ferromagnetic state for x = 0.10 and a cluster spin-glass state for x = 0.25.