Exchange Bias Effect in NdFeO3 System of Nanoparticles

We study the effect of nanometric size on the crystal structure, magnetic environment of iron and magnetization in NdFeO3 system of nanoparticles. The average particle size of NdFeO3 nanoparticles increases with annealing at 600 degrees C from about 15 nm to 40 nm, The smallest particles on annealed sample have size approximately 30 nm and typically have character of single crystalline samples. All samples adopt orthorhombic crystal structure, space group Prima with lattice parameters a = 5.5817 angstrom, b = 7.7663 angstrom and c = 5.456 angstrom for as prepared sample. The presence of superparamagnetic particles was indicated by the Mossbauer measurements. The reduction of dimensionality induces a decrease of T-N1 from 691 K to 544 K. The shift of magnetic hysteresis loop in vertical and horizontal direction was observed at low temperatures after cooling in magnetic field. We attribute such behaviour to exchange bias effect and discuss in the frame of core shellmodel.