Memory-functionality superconductor/ferromagnet/superconductor junctions based on the high- T c cuprate superconductors YBa 2 Cu 3 O 7 − x and the colossal magnetoresistive manganite ferromagnets La 2 / 3 X 1 / 3 MnO 3 + δ ( X = Ca , Sr )

Complex oxides exhibit a variety of unusual physical properties, which can be used for designing novel electronic devices. Here we fabricate and study experimentally nanoscale superconductor/ferromagnet/ superconductor junctions with the high-T c cuprate superconductors YBa 2 Cu 3 O 7−x and the colossal magnetoresistive (CMR) manganite ferromagnets La 2/3 X 1/3 MnO 3+δ (X=CaorSr). We demonstrate that in a broad temperature range the magnetization of a manganite nanoparticle, forming the junction interface, switches abruptly in a monodomain manner. The CMR phenomenon translates the magnetization loop into a hysteretic magnetoresistance loop. The latter facilitates a memory functionality of such a junction with just a single CMR ferromagnetic layer. The orientation of the magnetization (stored information) can be read out by simply measuring the junction resistance in a finite magnetic field. The CMR facilitates a large readout signal in a small applied field. We argue that such a simple single-layer CMR junction can operate as a memory cell both in the superconducting state at cryogenic temperatures and in the normal state up to room temperature.