Study on the structure and magnetic properties of Er3+-doped Li0.5Cr0.1Fe2.4−xEr _<i>x</i> O ₄ spinel ferrites

Engineering the interplay between lattice structure and magnetism is critical for developing next-generation functional materials. Here, we demonstrate that strategic, low-concentration doping of erbium (Er[Formula: see text] into a lithium-chromium ferrite (Li[Formula: see text]Cr[Formula: see text]Fe[Formula: see text]Er x O 4 , [Formula: see text]–0.05) offers an effective method to manipulate its magneto-structural landscape. Rietveld refinement of X-ray diffraction (XRD) data confirms that Er[Formula: see text] ions preferentially substitute Fe[Formula: see text] at octahedral (B) sites within the P4 3 32 spinel structure. This substitution induces a cascade of predictable structural changes, including lattice expansion and a controlled increase in lattice microstrain, which in turn kinetically suppresses grain growth. This structural evolution is mirrored in the XRD patterns, where the main (311) diffraction peak progressively broadens and shifts to lower angles. Notably, we uncovered a non-monotonic magnetic response. An optimal doping level ([Formula: see text]) is found to markedly enhance the A–B superexchange interaction, driven by an ideal degree of lattice distortion, which results in a striking increase in saturation magnetization ([Formula: see text], magnetocrystalline anisotropy ([Formula: see text], and Bohr magneton number ([Formula: see text]. Beyond this critical point, excessive doping leads to the precipitation of a minor ErFeO 3 phase and severe grain refinement. These factors collectively disrupt magnetic ordering and degrade performance. These findings establish a clear design principle: targeted structural modulation via low-concentration doping can be precisely harnessed to enhance the soft magnetic properties of spinel ferrites.