Electrical-transport, Magnetoresistance and Magnetic Properties of La0.7Ca0.3MnO3 and La0.7Ca0.24Sr0.06MnO3 Single Crystals

We report the electrical-transport, magnetoresistance and magnetic properties of the hole doped La0.7Ca0.3MnO3 (LCMO) and La0.7Ca0.24Sr0.06MnO3 (LCSMO) single crystals. It was prepared using floating zone technique. The resistivity data shows the metal to insulator transition (T-MI) occurs at 211 K along c-axis and T-MI = 185 K the ab-plane for LCMO and T-MI = 290 K along the c-axis and T-MI = 280 K along the ab-plane for LCSMO single crystals. It is observed that the T-MI is higher along the c-axis as compared to that in the ab-plane, consequently signifying more favorable hoping of electrons is along the c-axis. The ac-susceptibility measurement shows that this material exhibits ferromagnetic to paramagnetic transition temperature (T-C) at 206 K for LCMO and T-C = 277 K for LCSMO single crystals. For magnetic memory device application point of view, the sample shows the maximum MR of 98% for LCMO and 80% for LCSMO single crystals at 8T applied magnetic field. Doping small amount of Sr (0.06%) reveals that the electronic and magnetic phase transition in CMR single crystal increases substantially and useful for device application. This is first time such type of comparative study in these manganite single crystals.