Effect of Ga doping for Mn on the magnetic properties ofLa0.67Ca0.33MnO3

Abstract

The effect of Ga substitution for Mn in the ferromagnetic manganite ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ has been studied by preparing a series of ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{O}}_{3}$ $(x=0,0.10,0.25).$ 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 ${\mathrm{Mn}}^{3+}$ by nonmagnetic ${\mathrm{Ga}}^{3+}$ 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 ${\mathrm{Mn}}^{3+}$ and ${\mathrm{Ga}}^{3+}.$ 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 $x=0.25.$