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Title: Transport in ferromagnet/superconductor spin valves

Publication Date:
Sponsoring Org.:
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Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 5; Related Information: CHORUS Timestamp: 2017-02-08 22:09:06; Journal ID: ISSN 2469-9950
American Physical Society
Country of Publication:
United States

Citation Formats

Moen, Evan, and Valls, Oriol T. Transport in ferromagnet/superconductor spin valves. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.054503.
Moen, Evan, & Valls, Oriol T. Transport in ferromagnet/superconductor spin valves. United States. doi:10.1103/PhysRevB.95.054503.
Moen, Evan, and Valls, Oriol T. Wed . "Transport in ferromagnet/superconductor spin valves". United States. doi:10.1103/PhysRevB.95.054503.
title = {Transport in ferromagnet/superconductor spin valves},
author = {Moen, Evan and Valls, Oriol T.},
abstractNote = {},
doi = {10.1103/PhysRevB.95.054503},
journal = {Physical Review B},
number = 5,
volume = 95,
place = {United States},
year = {Wed Feb 08 00:00:00 EST 2017},
month = {Wed Feb 08 00:00:00 EST 2017}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevB.95.054503

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  • We report on large magnetoresistance in ferromagnet/superconductor/ferromagnet trilayer structures made of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and YBa{sub 2}Cu{sub 3}O{sub 7}. We find that the shape and height of the magnetoresistance peaks are not modified when the relative orientation of current and magnetic field is changed from parallel to perpendicular. Furthermore, we find that the temperature shift of the resistance curves is independent of current and of the sweep rate of the magnetic field. These observations favor the view that the magnetoresistance phenomenon originates in the spin dependent transport of quasiparticles transmitted from the ferromagnetic electrodes into the superconductor, and rulemore » out interpretations in terms of spontaneous vortices or anisotropic magnetoresistance of the ferromagnetic layers.« less
  • By applying an extended eight-component Bogoliubov–de Gennes equation, we study theoretically the tunneling conductance in clean ferromagnet/ferromagnet/iron pnictide superconductor (FM/FM/iron-based SC) heterojunctions. Under the condition of noncollinear magnetizations, twofold novel Andreev reflections exist due to the existence of two bands in the SC, in which the incident electron and the two Andreev-reflected holes, belonging to the same spin subband, form twofold spin-triplet pairing states near the FM/iron-based SC interface. It is shown that the conversions of the conductance not only between the zero-bias peak and valley at zero energy but also between the peaks and dips at two gap energiesmore » are strongly dependent on both the interband coupling strength in the SC and the spin polarization in the FM. The qualitative differences from tunneling into a conventional s-wave SC are also presented, which may help with experimentally probing and identifying the antiphase s-wave pairing symmetry in the iron-based SC. -- Highlights: •An eight-component Bogoliubov–de Gennes (BDG) equation. •Twofold novel ARs and twofold usual ARs. •Conversions of conductance between the zero-bias peak and valley at zero energy. •Conversions of conductance between peaks and dips at two gap energies. •The importance of the interband coupling strength in the SC.« less
  • Local magnetoresistance (MR) through silicon (Si) and its bias voltage (V{sub bias}) (bias current (I{sub bias})) dependence in ferromagnet (FM)/MgO/silicon-on-insulator lateral spin valves are investigated. From the experimental measurements, we find that the local-MR through Si increases with increasing V{sub bias}. This anomalous increase of local-MR as a function of V{sub bias} can be understood by considering the standard drift-diffusion theory improved by taking into account the difference in the interface resistances and first order quantum effect between FM/MgO/Si (source) and Si/MgO/FM (drain) interfaces. The interface resistance dependence on experimentally obtained local-MR ratios also agrees with the improved standard spinmore » diffusion theory. These results indicate that experimentally observed local-MR is certainly related to the spin signal through the Si bulk band.« less
  • We report interfacial characterization of 3,4,9,10-perylene-teracarboxylic dianhydride (PTCDA)-based organic spin valves (OSV) dusted with a thin layer of partially oxidized alumina at the organic semiconductor (OSC)/ferromagnet (FM) interfaces. Up to 13.5% magnetoresistance is achieved at room temperature. X-ray photoelectron spectroscopy measurements reveal interfacial electronic interaction between PTCDA and FM while the application of a thin alumina layer at the PTCDA/FM interfaces prevents the electronic hybridization and effectively preserves the spin injection into the OSC spacer. This finding demonstrates the critical effect of interfacial structure on magnetotransport behavior in OSV.