Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

Polycrystalline Gd0.15Ca0.85MnO3 sample was prepared by solid state reaction method and nanocrystalline samples of different grain sizes of the same were prepared by sol-gel method. Phase purity and composition were verified by room temperature X-ray diffraction and SEM-EDAX analysis. Magnetization data of bulk Gd0.15Ca0.85MnO3 in 5 kOe field shows a peak at ~119 K (TN) suggesting an antiferromagnetic transition. Nanocrystalline Gd0.15Ca0.85MnO3 sample (~54 nm size) also shows a cusp at ~107 K and a broad thermal hysteresis between field cooled cooling (FCC) and field cooled warming (FCW) data around this temperature. This thermal hysteresis suggests possible crystal structural transition. Field variation of magnetization of bulk Gd0.15Ca0.85MnO3 at 5 K shows a tendency to saturate, but yields a magnetic moment value of only ~1.12 μB/f.u. in 70 kOe. The value of magnetization of nanocrystalline sample at 5 K in 70 kOe field is slightly larger and is ~1.38 μB/f.u. which is probably due to the surface moments of the nanoparticle samples. Both the samples show Curie-Weiss-like behaviour in their paramagnetic state.