Nano-structured SmFeAs(O,F) single crystals: Nearly isotropic transport up to 65 T

Electric 4-probe transport measurements were performed on Focused Ion Beam (FIB) cut single crystals with sub-$\mu$m$^2$ cross-section, with current along and perpendicular to the crystallographic c-axis. The 4-probe geometry was defined accurately, resulting in large signals and excellent signal-to- noise ratio. Our study of the transport properties of SmFeAs (O,F) (T$_c$ $\approx$ 52 K) single crystals reveals a promising combination of high ($>$ 2 10$^6$ A/cm$^2$) and nearly isotropic critical current densities, which agree well with magnetization measurements. We find the onset of resistivity in pulsed fields up to 65T for currents along the c-axis (jIIc) very close to those for currents in the ab-plane. This favorable intragrain current transport in SmFeAs(O,F) is a crucial requirement for possible applications.