Exchange bias effect in La1-xAgxMnO3 nanopowders

Abstract

Exchange bias (EB) phenomena were first observed in the La 1-xAgxMnO3 as prepared and heat treated (300°C/2 hours) nanopowders (x = 0.10, 0.15 and 0.20) which were synthetized by self-combustion glycine-nitrate method. These nanoparticles have an average size of about 25 nm and adopt orthorhombic Pnma crystal structure. Cooling in magnetic field Hcf ≠ 0 through the Curie temperature TC shifts hysteresis loop in horizontal and vertical direction. The values of exchange bias field HE, coercive field Hc, remnant asymmetry μE and coercive magnetization μc increase with increasing value of cooling field Hcf. In addition the training effect was observed. Basic magnetic properties like the Curie temperature T C and the saturated magnetization μs increase and HE or μE decrease with heat treatment. Heat treatment at 600°C/2 hours increases the average size of nanoparticles to about 55 nm, crystal structure changes to rhombohedral structure (space group R3c) and EB effect vanishes. © 2013 Owned by the authors, published by EDP Sciences.