LAUSR

Abstract The microstructure, defect and magnetic properties of Ge-substituted CuFeO2 multiferroics are studied systematically. The introduction of Ge4+ in Fe3+ sites of CuFeO2 leads to obvious changes in its crystal structure, micro-morphology and surface chemical status. Positron annihilation results show that the concentration of positron traps and the local electron density increases evidently inside CuFe1−xGexO2 (x ≥ 0.05) series compare with that of un-doped sample. Interestingly, the magnetic hysteresis loops show the magnetic interactions are changed and obvious ferromagnetism appears in the CuFe1−xGexO2 (x ≥ 0.05) samples. In addition, the stability of the antiferromagnetic phase of CuFeO2 is weakened. The magnetic transition temperature TN2 slightly decreases with increasing Ge content. The relation between the microstructure and the magnetic behavior are explored in detail in the present paper.