Electrical-transport, Magnetoresistance and Magnetic Properties of La_(0.7)Ca_(0.3)MnO_3 and La_(0.7)Ca_(0.24)Sr_(0.06)MnO_3 Single Crystals

摘要

We report the electrical-transport, magnetoresistance and magnetic properties of the hole doped La_(0.7)Ca_(0.3)MnO_3 (LCMO) and La_(0.7)Ca_(0.24)Sr_(0.06)MnO_3 (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.