Electrical-transport, magnetoresistance and magnetic properties of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and La{sub 0.7}Ca{sub 0.24}Sr{sub 0.06}MnO{sub 3} single crystals
We report the electrical-transport, magnetoresistance and magnetic properties of the hole doped La{sub 0.7}Ca{sub 0.3}MnO{sub 3} (LCMO) and La{sub 0.7}Ca{sub 0.24}Sr{sub 0.06}MnO{sub 3} (LCSMO) single crystals. It was prepared using floating zone technique. The resistivity data shows the metal to insulator transition (T{sub MI}) occurs at 211 K along c-axis and T{sub MI} = 185 K the ab-plane for LCMO and T{sub MI} = 290 K along the c-axis and T{sub MI} = 280 K along the ab-plane for LCSMO single crystals. It is observed that the T{sub 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 (TC) at 206 K for LCMO and T{sub 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.