STRUCTURAL AND MAGNETIC-PROPERTIES OF YBA2FE3O7+X - FE-BASED 1-2-3 CERAMIC OXIDE

The YBa2Fe3O7+x (x = 0.69) compound, synthesized through normal ceramic routes, is found to have an orthorhombic structure (Pmmm, a = 3.9078(11), b = 3.9406(4), c= 11.7292(37)) with Fe3+ occupying two nonequivalent sites (1a and 2q). Mossbauer studies (MES) reveal an AFM order with a B(eff) that follows a S = 5/2 Brillouin function, giving B(eff)(T = 0) = (48.5 +/- 0.5) T and T(N) = (1020 +/- 10) K. Due to their highly symmetric character, the (6S) Fe3+ ions are insensitive to their surrounding electronic environment, consequently a single set (rather than two sets) of hyperfine parameters, is reflected in MES spectra. Based on the above results, as well as on data published, some comments are given regarding the interpretation of the MES results of the much studied YBa2(Cu(1-y)Fe(y))3O7-z system.