Sol-gel synthesis and structural evolution in solid solutions of InGaZn1-xCoxO4 (0 ≤ x ≤ 1)

Complete solid solutions InGaZn1-xCoxO4 (0 < x < 1) were synthesized via the citrate sol-gel method and structurally characterized by powder X-ray diffraction. All oxides adopt the LuFe2O4-type layered structure and crystallize in the space group R3m. The successful cationic doping can be first confirmed by the linear changes in a- and c-axes lengths, then investigated by careful Rietveld refinements. The Co2+-to-Zn2+ replacement induces the structural changes in the [MO]2 (M = Ga, Zn, Co) layers exclusively, where M locates in the trigonal bipyr-amidal (TBP) coordination. In detail, three M-Obasal bond exhibit a gentle expansion, and two apical M-O bonds show opposite variations (a minor expansion and a severe contraction) with an overall decreasing in length. Interestingly, the latter one is likely due to the so-favored AFM interactions between Co2+-Co2+ couples along edge-shared TBPs. The temperature-dependent magnetic susceptibility confirms the very strong AFM interactions, however no magnetic order can be established above 5 K.