Magneto-structural Imprints in Eu-Substituted NdCrO _3 Perovskites

The chemical pressure-induced magneto-structural changes were investigated in Nd _1-x Eu _x CrO _3 with 0.2 ≤ x ≤ 1.0 compounds. The magnetic study shows the decrease of antiferromagnetic transition temperature ( T_N ) ∼ 220.7 K ( x = 0.2) to 182.5 K ( x = 1.0) due to the modification of Cr-Cr interaction. The spin-reorientation transition ( T _SR ) exhibits for all samples except x = 1.0 with a decrease from ∼ 40.1 K ( x = 0.2) to 13.3 K ( x = 0.9). We observed the exchange bias (EB) effect and the EB field decreases with increasing Eu content. The chemical pressure boundary at x = 0.5 is marked and the lattice softens on both sides of this substitution. The magnetoelastic coupling below T_N is revealed by the temperature dependence of the lattice parameters, Cr-O lengths, Cr-O-Cr angles, and Nd/Eu positions for x < 0.5 samples. We have reported the electron density distribution using the maximum entropy method for the first time in the Nd _1-x Eu _x CrO _3 compound. Interestingly, we found a structural reorientation around ∼ 80 K between T_N and T _SR from a centrosymmetric structure ( Pnma ) with unstable electron density to a stable noncentrosymmetric (Pna2_1) structure.