Reversal magnetization and exchange bias effect of the nanocrystalline Yb1-xPrxCrO3 solid solution

Abstract

Polycrystalline samples of Yb1-xPrxCrO3 (0 ≤ x ≤ 1) were synthesized in the whole solubility range by auto-ignition high-temperature synthesis. TEM images revealed a particle size of about 20–25 nm in the solid solution for as-combustion powders. The crystal structure and the chemical state of the cations were characterized by a combination of X-ray diffraction method and X-ray photoelectron spectroscopy. It is found a complete solubility of the Pr ions and a mixed valence state in the Yb-rich composition range (Yb1-xPrxCrO3; 0 < x < 0.5). There, the presence of Yb2+ ions is compensating by the Pr4+ valence states. Besides, the spectroscopy results found a mix of Cr3+ and Cr6+ valence states in the solid solution. Temperature dependence of DC-magnetization measurements showed that the antiferromagnetic transition increases almost linearly from ~ 119 for YbCrO3 to ~ 243 K for PrCrO3. Furthermore, the magnetization reversal observed in the YbCrO3 is progressively weakened with increasing Pr content and disappears for x = 0.30 of Pr substitution. The isothermal magnetization measured below of TN1 and TN2 (2 K) found that the weak ferromagnetism is canceled in the YbCrO3 magnetic ground state. Opposite to this behavior, the end PrCrO3 composition showed a defined magnetic hysteresis loop which infers a weak ferromagnetic component in the magnetic ground state. Besides, the M–H curves showed a negative exchange bias (EB) effect induced by Pr substitution, which is observed above of x = 0.04, and being more intense for x = 0.10 of Pr composition. The vanishing magnetization reversal and exchange bias effect are influenced strongly by the weak ferromagnetic component arising from PrCrO3 sub-lattice in solid solution. The results demonstrate once again, the importance of the interaction between Dzyaloshinsky–Moriya and single-ion anisotropy in the orthochromite family. Also, the results here could stimulate research toward understanding the magnetic ground state whose investigations below TN2 are scares in both compounds.