Size-dependence of the exchange bias effect observed in Nd1-xDyxCrO3 (x = 0.05 and 0.20) compounds

Abstract The particle-size effects on the exchange bias phenomenon have been investigated in perovskite Nd 1 - x Dy x CrO 3 (x = 0.05 and 0.20) compounds, which are obtained via co-precipitation method. The analysis of the X-ray diffraction data through Rietveld refinement show that, independently of calcination temperatures and nominal compositions, samples exhibit a single phase with orthorhombic structure and Pnma space group. The calculated particle average diameters via Scherrer formula range from 50 to 90 nm. The magnetic-field and T-dependencies of magnetization using the field-cooled-cooling protocol are performed. For all samples, the MvsT curves present a first magnetic transition at T ≈ 210 K likely associated with the antiferromagnetic order of Cr 3 + ions and a second one at T ≈ 40 K assigned to their spin reorientation. Magnetic hysteresis loops show the presence of a negative exchange bias phenomenon for all samples, whose values of exchange bias field, H EB , decrease with increasing particle size. We argue that this behavior is mainly associated to the uncompensated surface spins, which are dependent on the particle size.