RESUMO
The atomic-scale degree of B/B' alternate cationic disorder is known to significantly influence the macroscopic properties of the quadruple perovskites AA3'B2B2'O12; however, the nature of this disorder has rarely been critically studied. Herein, the effect of B-site cationic arrangement on the electronic and magnetic properties of the quadruple perovskite CaCu3Fe2Nb2O12 was systemically investigated using the first-principles calculations. The results demonstrate that the B-site ordered CaCu3Fe2Nb2O12 is a ferrimagnetic insulator with antiferromagnetic coupling between the A'-site Cu and B-site Fe. The calculated total magnetic moment is 7.00 µB f.u.-1, which is apparently larger than the experimentally measured saturation magnetization because of different degrees of the B-site disorder. Furthermore, the electronic structures illustrate that the magnetic moments sharply decrease with an increase in the B-site antisite defects, i.e., the total magnetic moments obviously reduce with an increase in the B-site Fe/Nb disorder, and ultimately, no magnetism is observed. Interestingly, the B-site antisite defects not only introduce Fe-Fe antiferromagnetic coupling, but also induce the antiferromagnetic arrangement of Cu spins in the totally disordered structure. Cu-Fe and Fe-Fe magnetic coupling competition is coupled with antisite defects, and finally, Fe-Fe antiferromagnetic coupling turns into the dominating spin coupling in the disordered CaCu3Fe2Nb2O12. Moreover, the B-site antisite defects do not alter the insulator nature of the perovskite despite the significantly narrowed band gap. Our study opens up a novel avenue for the straightforward understanding of the effect of cationic ordering on the electronic and magnetic properties of quadruple perovskites and offers an additional opportunity for tailoring their characteristics.