Structure and properties of EuZnGa

New ternary gallide EuZnGa was synthesized by reaction of the elements in a sealed tantalum tube at 1320 K and subsequent annealing at 970 K for seven days. EuZnGa was investigated by X-ray diffraction on both powders and sin gle crystals. Its structure was refined from single crystal diffractometer data: KHg2 type, space group Imma, a = 461.7(2), b = 761.4(3), c = 777.0(3) pm, R = 0.041 for 486 structure factors and 13 variables. The zinc and gall ium atoms statistically occupy the mercury position of the KHg2 type of str ucture. No long-range ordering between the zinc and gallium atoms could be detected from the X-ray data. Magnetic susceptibility measurements show Cur ie-Weiss behavior above 50 K with a magnetic moment of mu (exp) = 7.86(5) m u (B)/Eu and Theta = 17(2) K, suggesting divalent europium. Low-field, low- temperature susceptibility measurements indicate cluster glass behavior (mi ctomagnetism) with a freezing temperature of 24(2) K. Magnetization measure ments show a magnetic moment of 4.9(1) mu (B)/Eu at 2 K and a magnetic flux density of 5.5 T. Electrical resistivity data indicate metallic behavior. Eu-151 Mossbauer spectroscopic measurements show onset of magnetic hyperfin e splitting at less than or equal to 17.0 K. Down to the temperature of 4.2 K the spectra reflect magnetic relaxation effects suggesting the presence of a substantial extent of disordering. This observation is consistent with the cluster glass behavior as evident from the magnetic susceptibility dat a and may be a consequence of the presence of multiple local Eu sites as ex pected from the statistical Zn and Ga distribution over the corresponding s ites in the KHg2 structure.