NEW TERNARY BORIDE EuRh_4B_4 SYNTHESIZED UNDER HIGH PRESSURE AND TEMPERATURE

摘要

We report the results of a detailed study of EuRh_4B_4 compound synthesized by an uncommon method under high pressure - temperature conditions for the first time. Synthesized sample has been initially characterized by X-ray diffraction, macroscopic electrical resistivity and ac-susceptibility methods. The ferromagnetic and superconducting phases were found below 83K and 5.8K respectively. Element- and shell-selective XANES and XMCD techniques have been further applied to check the possible valence transition of Eu ions and their magnetic states. XANES spectra recorded at the Eu L_(2,3) absorption edges clearly indicate the presence of either "magnetic" Eu~(2＋) or "non-magnetic" Eu~(3＋) ions in the sample. The XMCD studies have also shown that local magnetic moments of Eu~(2＋) ions exist in the superconducting EuRh_4B_4, at least above the transition.