Estudo das propriedades estruturais e magnéticas do sistema Nd1-xTbxCrO3

Abstract

In this work the structural and magnetic properties of the rare earth orthocromites Nd1- xTbxCrO3 (0 ≤ x ≤ 1) obtained by the co-precipitation method are studied. The samples are characterized through X-ray diffraction (XRD) measurements and analised using the Rietveld refinement method. Magnetization measurements as a function of temperature (MxT) and magnetic field (MxH) are corried out. All samples crystallize in the perovskite structure with orthorhombic symmetry, space group Pnma. The lattice parameters, Cr-Cr distances, and Cr- O-Cr angles schow slight but systematic modifications depending on the concentration of Tb3+. The MxT curves show a decrease in the antiferromagnetic transition temperature (TN) of the Cr3+ sub-lattice with increasing Tb3+ concentration. Additionally, the spin reorientation temperature (TRS) is suppressed at higher Tb3+ concentrations. MxH measurements conducted at temperatures above TRS reveal the presence of an antiferromagnetic state accompanied by a weak ferromagnetic contribution. In contraast, MxH measurements below the TRS show the absence of canted antiferromagnetism,, indicating a magnetic transition from the Γ2 (Fx, Cy, Gz) phase to the Γ1 (Ax, Gy, Cz) phase. The samples with x = 1 and x = 0.9 did not exhibit TRS, remaining in the Γ2 (Fx, Cy, Gz) phase. Exchange Bias (EB) was also observed in samples with lower Tb3+ concentrations. These results suggest that doping with the non-Kramers ion Tb3+ plays an important role in determining the total magnetization of the rare earth sub-lattices, indicating that the presence of a weak ferromagnetic component combined with the polarization of the rare earth site (TR) is necessary for the emergence of EB.