Regulation of Cr³⁺ doping on the defect characteristics and magnetic order in the CuFe_1-xCr_xO₂ ceramics

Abstract

The defect characteristic and magnetic properties of CuFe 1-x Cr x O 2 (x = 0.0-0.4) compounds have been investigated in detail. The results demonstrate that Cr 3+ ions enter into the CuFeO 2 lattice sites and induce local lattice contraction but do not change the valance state of Cu + and Fe 3+ ions. We calculate the positron annihilation lifetime in the bulk and vacancy defect trapping states by the atomic superposition method in 3 × 3 × 1 CuFeO 2 super-cell. Combined with theoretical calculation results, the positron annihilation results indicate that the positrons are mainly annihilated in vacancy clusters in CuFe 1-x Cr x O 2 . The substitution of Cr 3 + for Fe 3+ ions decreases the open volume and increases the concentration of vacancy defects but does not change the integral defect surroundings at annihilation sites. Magnetization measurements manifest that doping with Cr 3+ reduces the antiferromagnetic transition temperature and promotes the formation of short-range magnetic correlation. Meanwhile, the enhanced short-range magnetic correlation in Cr 3+ -doped CuFeO 2 is more readily driven by thermal activation energy and a faster dynamic behavior can be seen in time windows.

Doping‐Dependent Phase Fractions in Hydrothermally Synthesized Mn‐Doped CuFeO2

“…Even if defects in delafossites, in general, and , in particular, have not been extensively studied, it is known that antisite defects, interstitial oxygen, and vacancies are major contributors. [ 34–36 ] Besides, in a study on CuAlO 2 significant off‐stoichiometries of all constituents were reported after hydrothermal synthesis. [ 34 ] The low formation energy of antisite defects, i.e., Cu on the Fe site, in [ 35 ] might thus render those defects to be intrinsic antagonists to Mn doping.…”