Structural, magnetic and electronic properties of pulsed-laser-deposition grown SrFeO_3−δ thin films and SrFeO_3−δ/La_2/3Ca_1/3MnO₃ multilayers

We studied the structural, magnetic and electronic properties of ${SrFeO}_{3-\delta }$ (SFO) thin films and ${SrFeO}_{3-\delta }$/${La}_{2/3}$ ${Ca}_{1/3}$MnO₃ (LCMO) superlattices that have been grown with pulsed laser deposition (PLD) on ${La}_{0.3}$ ${Sr}_{0.7}$ ${Al}_{0.65}$ ${Ta}_{0.35}$ $O_3$ (LSAT) substrates. X-ray reflectometry and scanning transmission electron microscopy (STEM) confirm the high structural quality of the films and flat and atomically sharp interfaces of the superlattices. The STEM data also reveal a difference in the interfacial layer stacking with a SrO layer at the LCMO/SFO and a LaO layer at the SFO/LCMO interfaces along the PLD growth direction. The x-ray diffraction (XRD) data suggest that the as grown SFO films and SFO/LCMO superlattices have an oxygen-deficient ${SrFeO}_{3-\delta }$ structure with I4/ mmm space group symmetry ($\delta ⩽0.2$). Subsequent ozone annealed SFO films are consistent with an almost oxygen stoichiometric structure ($\delta \approx 0$). The electronic and magnetic properties of these SFO films are similar to the ones of corresponding single crystals. In particular, the as grown ${SrFeO}_{3-\delta }$ films are insulating whereas the ozone annealed films are metallic. The magneto-resistance effects of the as grown SFO films have a similar magnitude as in the single crystals, but extend over a much wider temperature range. Last but not least, for the SFO/LCMO superlattices we observe a rather large exchange bias effect that varies as a function of the cooling field. (paper)