Abstract Single phase TmB12, YbB12 and LuB12 were successfully obtained by the arc-melting and floating zone methods. The XPS measurements of these compounds have indicated that (1) only YbB12 is a valence fluctuating compound with the valency of +2.9 at room temperature, (2) the correlation energy between Yb2+ and Yb3+ ions is about 6.0 eV, (3) Tm and Lu ions in the dodecaborides are in a trivalent state
We present measurements of the magnetization and electrical resistivity of TmB12, ErB12 and HoB12 singlecrystalline samples as well as of a DyB12 polycrystalline sample. Data were taken in the paramagnetic state as well as in the magnetically ordered regime. To our knowledge, this is the first systematic investigation of TmB12, ErB12, HoB12 and DyB12 on the magnetically ordered phase by measurements of magnetization and electrical resistivity. All samples investigated undergo antiferromagnetic ordering in the lower Kelvin temperature range. From the magnetization data, the Neel temperatures, the paramagnetic Curie temperatures, and the effective magnetic moments of the corresponding rare earth ions are determined. It is shown that the indirect exchange interaction of RKKY type is the dominating mechanism leading to the observed antiferromagnetic ordering. The measured temperature dependences of the electrical resistivity show a pronounced effect of superzone boundaries near Neel temperatures. The spin wave scattering of conduction electrons below T-N is discussed, too. (C) 1999 Elsevier Science B.V. All rights reserved.