Negative magnetization in the zero field-cooled and exchange-bias effect in Cu-doped PrCrO3

High-quality nanometric and homogeneous particles of Cu–doped PrCrO3 ceramic compounds were synthesized by the hydrothermal-assisted sol–gel method. Structural, chemical state, morphology, and magnetic properties were investigated in the PrCr1−xCuxO3 orthochromite with 0 ≤ x ≤ 0.1 composition. XRD patterns show a complete solubility of the Cu ion, as well as an increase of the orthorhombic cell volume. The microstructural analysis (SEM) shows that the nanometric-size particles obtained from the synthesis process coalesce during the subsequent high-temperature process. In addition, XPS analysis revealed that the solubility and charge compensations by aliovalent Cu2+ ions substitution are driven by the change of the oxidation state from Cr3+ to Cr5+ and Cr6+. These results produce novel changes in the magnetic properties. There, the ZFC-mode shows negative magnetization in all investigated samples, and it is discussed as an intrinsic phenomenon in terms of the Γ2 (Fx, Cy, Gz) spin configuration as well as the arising of the diamagnetic Cr6+ (do). It is noted that Cr6+ tunes the diamagnetic magnitude during the ZFC protocol. On the other hand, different oxidation states are observed at the Cr site in PrCrO3, whose final result is an increase of the coercivity field, Hc, and the remanent magnetization, Mr, in the M–H curves. The increase of ferromagnetic and the antiferromagnetic domains sharing the same volume leads to an anisotropic magnetic interaction, called exchange-bias effect. It is observed that the Cu-doped PrCrO3 decreases the exchange-bias effect, but at the same time an increase in the magnetic properties is observed at 2 K.