Structural and magnetic investigation of Fe3+ and Mg2+ substitution into the trigonal bipyramidal site of InGaCuO4

Abstract

The solid solutions of InGa1−xFexCuO4, InFeCu1−xMgxO4, and InGa1−xFexCu1−xMgxO4 were synthesized and characterized through the use of X-ray and neutron diffraction, and DC—magnetism measurements. All compositions of InGa1−xFexCuO4 are single phase and crystallize in the R3¯m space group, but a transformation to the spinel InFeMgO4 structure was observed for the other series of Fe3+ and Mg2+—rich compounds. As a result of the similar ionic radii for Ga3+ and Fe3+, there was not an obvious change in the c/a ratio for InGa1−xFexCuO4. In the hexagonal domains, the c/a ratio of InFeCu1−xMgxO4 and InGa1−xFexCu1−xMgxO4 showed a linear trend that can be explained by the change in electronic configurations between Cu2+ and Mg2+. All hexagonal compositions display negative Weiss temperatures, and there is an increase in the magnetic transition temperature with the addition of Fe3+. Additional AC magnetic susceptibility measurements for the x=0.4 and 0.6 compositions within the InGa1−xFexCuO4 solid solution show that these transitions are consistent with spin glass behavior, not long range AFM ordering.