The Structural, Optical, and Magnetic Properties of in CuFe 0.95 M 0.05 O 2 Delafossites ( M =transition metal)

In this paper, M (Sc 3+ and Zr 4+ )-doped CuFeO 2 ceramics were prepared by using a solid-state reaction method. The effects of isovalent Sc 3+ and nonisovalent Zr 4+ substitution on the structure, defects, optical, and magnetic properties of CuFeO 2 ceramics are comparatively investigated. The results demonstrated that all of the obtained samples are well crystallized, and M substitution leads to lattice structure distortion. The average grain sizes reduce with the addition of M . Positron annihilation lifetime results indicate that the vacancy clusters are present in all samples, and the Zr-substituted CFO sample has the maximum open volume and concentration of the defect among those three samples. Furthermore, the bandgap of the M -substituted samples becomes wider due to the broad bandgap of Sc 2 O 3 and ZrO 2 . M substitution enhances the Urbach energy ( E U ) values in CFO system, which is in good consistent with the dependences of the defect concentration on the substitution elements. The magnetic measurements reveal that Sc and Zr substitution decrease the magnetic temperatures T N1 and T N2 , which may be attributed to the consequence of the magnetic dilution effect and the change in the strength of exchange interaction. In addition, the defects are of major importance for regulating the magnetic properties of CFO ceramics.