Superconductors and ferromagnets are highly non-compatible materials due to the natures of their respective electronic states.But when artificially brought together,they develop interesting characteristics,one of whic...Superconductors and ferromagnets are highly non-compatible materials due to the natures of their respective electronic states.But when artificially brought together,they develop interesting characteristics,one of which,vortex clustering,is discussed here in this paper.Phase-field and micromagnetic simulations are performed to investigate the superconductor and ferromagnet bilayer,respectively.The ferromagnet with uniaxial anisotropy is observed to develop the maze domain,whereas the superconductor subjected to the influence of the ferromagnetic stray field displays a vortex pattern.Clustered vortices in superconductors at certain locations are observed to be precisely located over magnetic domain bifurcations.The enhanced out-of-plane stray field at bifurcations around the curved domain walls and the convergent Lorentz force due to screening currents in superconductor are attributed to the formation of clusters at bifurcation sites.Segregation of the inter-vortex spacing between straight and bifurcated domain is clearly observed.More importantly,inter-vortex spacing is predicted to serve as a precise tool to map local ferromagnet domain shapes.展开更多
Current superconducting memory devices lack the basic quality of high memory density for practical memories,mainly due to the size limitations of superconducting quantum interference devices.Here,we propose a supercon...Current superconducting memory devices lack the basic quality of high memory density for practical memories,mainly due to the size limitations of superconducting quantum interference devices.Here,we propose a superconductor–ferromagnet bilayer device with strain-pulse-assisted multi-bit ladder-type memory,by using strain-engineered ferromagnet domain structure to control carrier concentration in the superconductor,which is simulated by coupled Landau–Lifshitz–Gilbert and Ginzburg–Landau equations.Current-and strain-pulses are observed to deterministically control the resistivity of superconductor for one and two-bit device arrangements.The average carrier concentration of superconductor is observed to have multiple metastable states that can be controllably switched using current-pulse and strain-pulse to determine multiple resistivity states.These findings confirm the eligibility of superconductor–ferromagnet bilayers to be used as ladder-type multibit memories and open a new way for further theoretical and experimental investigations of the cryogenic memories.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51972028 and 12004036)the National Key Research and Development Program of China(Grant No.2019YFA0307900)。
文摘Superconductors and ferromagnets are highly non-compatible materials due to the natures of their respective electronic states.But when artificially brought together,they develop interesting characteristics,one of which,vortex clustering,is discussed here in this paper.Phase-field and micromagnetic simulations are performed to investigate the superconductor and ferromagnet bilayer,respectively.The ferromagnet with uniaxial anisotropy is observed to develop the maze domain,whereas the superconductor subjected to the influence of the ferromagnetic stray field displays a vortex pattern.Clustered vortices in superconductors at certain locations are observed to be precisely located over magnetic domain bifurcations.The enhanced out-of-plane stray field at bifurcations around the curved domain walls and the convergent Lorentz force due to screening currents in superconductor are attributed to the formation of clusters at bifurcation sites.Segregation of the inter-vortex spacing between straight and bifurcated domain is clearly observed.More importantly,inter-vortex spacing is predicted to serve as a precise tool to map local ferromagnet domain shapes.
基金Project sponsored by the National Natural Science Foundation of China(Grant Nos.52150410420 and 51972028)the National Key Research and Development Program of China(Grant No.2019YFA0307900)。
文摘Current superconducting memory devices lack the basic quality of high memory density for practical memories,mainly due to the size limitations of superconducting quantum interference devices.Here,we propose a superconductor–ferromagnet bilayer device with strain-pulse-assisted multi-bit ladder-type memory,by using strain-engineered ferromagnet domain structure to control carrier concentration in the superconductor,which is simulated by coupled Landau–Lifshitz–Gilbert and Ginzburg–Landau equations.Current-and strain-pulses are observed to deterministically control the resistivity of superconductor for one and two-bit device arrangements.The average carrier concentration of superconductor is observed to have multiple metastable states that can be controllably switched using current-pulse and strain-pulse to determine multiple resistivity states.These findings confirm the eligibility of superconductor–ferromagnet bilayers to be used as ladder-type multibit memories and open a new way for further theoretical and experimental investigations of the cryogenic memories.
