A suppression of superconductivity in the late rare-earth RFeAsO1-xFx materials is reported. The maximum critical temperature (T-c) decreases from 51 K for R=Tb to 36 K for HoFeAsO0.9F0.1, which has been synthesized under 10 GPa pressure. This suppression is driven by a decrease in the Fe-As-Fe angle below an optimum value of 110.6 degrees, as the angle decreases linearly with unit-cell volume (V) across the RFeAsO1-xFx series. A crossover in electronic structure around this optimum geometry is evidenced by a change in sign of the compositional dT(c)/dV, from negative values for previously reported large R materials to positive for HoFeAsO0.9F0.1.
|Number of pages||4|
|Journal||Physical Review B: Condensed Matter and Materials Physics|
|Publication status||Published - Aug 2009|