Memory-functionality superconductor/ferromagnet/superconductor junctions based on the high- Tc cuprate superconductors YBa2Cu3O7

Abstract

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 =Ca or Sr). 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.

Cryogenic Memory Element Based on an Anomalous Josephson Junction

“…Interestingly, by recalling the definition of the parameter ε = E J /(K Ω), from Eqs. (15) and (24) we can easily obtain the following relation between the normalized thermal noise intensities…”

“…One of the key challenges towards this objective is the fabrication of a reliable and scalable cryogenic memory architecture. Superconductor-ferromagnet-superconductor (SFS) junctions are promising structures suggested for such memories [6][7][8][9][10][11][12][13][14][15]. Indeed, the interplay between the intrinsic exchange field and the induced superconductivity in the ferromagnet leads to the so-called π-junction, i.e., a Josephson junction exhibiting an intrinsic π-phase shift in its ground state.…”

Magnetoelectric effects in Josephson junctions

“…One of the key challenges towards developing ultra-low-power computers is the fabrication of a reliable and scalable cryogenic memory architecture. Superconductorferromagnet-superconductor (S-F-S) junctions are promising structures suggested for such memories [142,143,[223][224][225][226][227][228][229][230][231][232][233]. The magnetization reversal by the electric current pulses discussed here has also been suggested as one of the possible realizations of the JJ-based cryogenic memory elements.…”

Magnetoelectric effects in Josephson junctions

“…of the key challenges towards developing ultra-low-power computers is the fabrication of a reliable and scalable cryogenic memory architecture. Superconductor-ferromagnet-superconductor (S-F-S) junctions are promising structures suggested for such memories 142,143,[223][224][225][226][227][228][229][230][231][232][233] . The magnetization reversal by the electric current pulses discussed here has also been suggested as one of the possible realizations of the JJ-based cryogenic memory elements.…”