Structural, Magnetic, and Electron Transport Studies on Nanocrystalline Layered Manganite La_1.2Ba_1.8Mn₂O₇ System

The structure property relationship for Ru doped La_1.2Ba_1.8Mn_2−x Ru _x O₇ system has been studied systematically. The system crystallizes in the single-phase tetragonal structure with space group of I _4/mmm. The unit cell volume is found to increase with Ru doping. The sheet type microstructure could be seen in this system, which is important for anisotropic nature of layered structure. The crystallite size is found to be 25 nm indicating nanocrystalline nature of the system. Ferromagnetic to paramagnetic (T _c) transition above the room temperature is observed in all except the highest doped Ru (x = 1.0) where the T _c is 254 K using a.c. susceptibility measurement. The large values of magnetoresistance for the x = 0.0 sample at 10 K is found to be 57% and 64% at applied fields of 5 and 10 T, respectively.