Exchange Bias Effect in La_1-xAg_xMnO₃ Nanopowders

¹ Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice, Slovak Republic
² Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków, Poland
³ Institute of Chemistry, Faculty of Science, P.J. Šafárik University, Moyzesova 11, 040 01 Košice, Slovakia

Abstract

Exchange bias (EB) phenomena were first observed in the La_1-xAg_xMnO₃ 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 H_cf ≠ 0 through the Curie temperature T_C shifts hysteresis loop in horizontal and vertical direction. The values of exchange bias field H_E, coercive field H_c, remnant asymmetry μ_E and coercive magnetization μ_c increase with increasing value of cooling field H_cf. In addition the training effect was observed. Basic magnetic properties like the Curie temperature T_C and the saturated magnetization µ_s increase and H_E or µ_E 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 ) and EB effect vanishes.