Modulation of magnetic and dielectric properties by Al3+ substitution in Ca3CoMnO6 ceramics

We report a detailed study of the influence of non-magnetic Al ³⁺ doping on the microstructure, magnetic, and dielectric characteristics Ca ₃CoMnO ₆. The introduction of Al ³⁺ leads to the suppression of competing short-range magnetic orders, a gradual disappearance of the spin freezing peak in Ca ₃CoMn _1-xAl _xO ₆ was observed, accompanied by the release of magnetic frustration. Moreover, a weakening of the antiferromagnetic order in Ca ₃CoMnO ₆ was attributed to the dilution effect induced by non-magnetic Al ³⁺ within the Co-Mn-Co-Mn spin chains. The dielectric measurements exhibit excellent agreement with the magnetic measurements. The substitution of Mn ⁴⁺ with Al ³⁺ results in the attenuation of relaxor ferroelectric behavior, accompanied by a decrease in the static freezing temperature T _f and an increase in the activation energy E _a. It indicates that Al ³⁺ substitution could well suppress the formation of polar nanoregions. With introducing Al ³⁺ the magnetodielectric effect of Ca ₃CoMnO ₆ is also significantly enhanced. For the x = 0.15 sample, the magnetodielectric effect undergoes a notable variation of approximately 10 % under a magnetic field of H = 4 T.