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

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 R3m 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

Structural and magnetic investigation of In₂Fe₂₋ₓGaₓCuO₇

The solid solution of In₂Fe₂₋ₓGaₓCuO₇ (space group P6₃/mmc) was synthesized and investigated through X-ray diffraction and magnetic susceptibility studies. Limited changes to the lattice parameters were observed as a result of the similar ionic radii for Fe³⁺ and Ga³⁺ in the trigonal bipyramidal (TBP) crystallographic site. An increase in the Weiss temperature, along with spin glass behavior are observed from x = 0 – 2, but irregularities in the trend are apparent for x = 0.75 and 1. With the highest concentration in magnetic ions, In₂Fe₂CuO₇ appears to have competing nearest neighbor interactions that produce a suppression of the Curie tail and the experimental magnetic moment. In comparison to InFe₁₋ₓGaₓCuO₄, both solid solutions show an invariable progression of the lattice parameters, but the magnetic properties are greatly affected by the distinct TBP layering schemes.Keywords: X – ray diffraction, Layered compounds, Trigonal bipyramidal coordination, Transition metal oxides, Magnetic propertiesKeywords: X – ray diffraction, Layered compounds, Trigonal bipyramidal coordination, Transition metal oxides, Magnetic propertie

Influence of Structural Disorder on Hollandites A_<i>x</i>Ru₄O₈ (A⁺ = K, Rb, Rb_1–<i>x</i>Na_<i>x</i>)

Structural disorder can play an important role in the electrical properties of correlated materials. In this work we examine the average and local disorder in hollandites A_<i>x</i>Ru₄O₈ (A⁺ = K, Rb, Rb_1–<i>x</i>Na_<i>x</i>) through neutron total scattering techniques. Samples with A⁺ = Rb, Rb_1–<i>x</i>Na_<i>x</i> exhibit the largest amount of local disorder as evidenced by higher atomic displacement parameters, and as a result, a weakened temperature dependence of the resistivity is observed upon cooling as compared to K_<i>x</i>Ru₄O₈. All samples exhibit anisotropic resistivity that is dominated by metallic conductivity at lower temperatures, and this is corroborated by Pauli paramagnetic behavior throughout the measured temperature regime