Direct observation of the microstructure in cluster glass compound U2IrSi3

We have examined the structure of a U2IrSi3 compound exhibiting ferromagnetic cluster glass behaviour by means of electron diffraction observation and high-resolution electron microscopy. The structure of U2IrSi3 has been proposed as a new one of the U2RuSi3-type with a short-range ordered double stacking sequence of the U2RuSi3-type structure along the c-axis, and long-range ordered atomic arrangements in the a-b plane. The calculated patterns reproduce the characteristic features of observed electron patterns well. The Fourier-filtered high-resolution image clearly exhibits a micro-domain structure, which is considered to relate directly to the origin of the observed cluster glass behaviour in U2IrSi3.