Structural and magnetic properties of the M{sub 2}Ga{sub 2}Fe{sub 2}O{sub 9} (M=In, Sc) oxides

We report on the structural and magnetic properties of In{sub 2}Ga{sub 2}Fe{sub 2}O{sub 9} and Sc{sub 2}Ga{sub 2}Fe{sub 2}O{sub 9}. X-ray diffraction measurements confirmed the presence of a single orthorhombic phase, corresponding to the expected structure for M{sub 2}Ga{sub 2}Fe{sub 2}O{sub 9} (M=In, Sc). Neutron diffraction measurements show considerable cation disorder at different lattice sites, and suggest that there is no long range magnetic ordering down to T=10 K. Temperature dependent magnetization measurements show a separation between field-cooled and zero-field-cooled curves near T{sub f}≈19 K. Below this temperature the M(H) curves also exhibit history dependent behavior. The temperature dependent ac susceptibility shows a peak in the magnetic dissipation, with the temperature of the peak varying systematically with frequency suggesting that this feature may be associated with a glassy relaxation. Zero-field specific heat measurements down to 4 K do not reveal any long range magnetic ordering of these compounds, nor is there any transition to an ordered state under the application of a 7 T field. - Graphical abstract: Temperature variation of magnetization (ZFC and FC) of M{sub 2}Ga{sub 2}Fe{sub 2}O{sub 9} (M=In, Sc) samples at 0.01 T. The magnetization has a history dependence with a bifurcation between ZFC and FCmore » data at the freezing temperature T{sub f}=19 K. The inset shows the enlargement for both oxides for temperatures below 30 K. Highlights: ► Chemical disorder study of the M{sub 2}Ga{sub 2}Fe{sub 2}O{sub 9} (M=In, Sc) compounds. ► Our study indicates for the first time a glassy magnetic ground state of this system. ► The glassy-like-behavior is due to magnetic frustration created by the site disorder.« less