Influence of Ti-doping on the magnetic exchange interaction of La0.5Ca0.5MnO3 nanoparticles.

The striking effect of Ti-doping on the magnetic properties of La 0.5 Ca 0.5 MnO 3 nanoparticles have been investigated by different methods. The half doped manganites are at the boundary between the ferromagnetic metallic and antiferromagnetic insulating phases. There is a delicate balance between ferromagnetic double exchange and antiferromagnetic superexchange interactions. In half doped La 0.5 Ca 0.5 MnO 3 charge ordered antiferromagnetic state is destabilized below a critical size followed by development of ferromagnetism. We have seen that slight disturbance in magnetic exchange interactions by Ti-substitution (>5%) drastically changes the fraction of ferromagnetic clusters. The ferromagnetic Mn 3+ —O—Mn 4+ interaction is suppressed by Mn 3+ —O—Ti 4+ type of interactions. For more than 10% Ti doping the surface ferromagnetic character of the nanoparticles is largely weighed down. This suppression of ferromagnetic component by diamagnetic Ti-doping eventually leads to phase separated states with lower magnetization value. [ABSTRACT FROM AUTHOR]