論文

Abstract Tunnel magnetocapacitance (TMC) ratios greater than 450% are observed at room temperature in epitaxial FeCo/MgAl2O4/FeCo(001) magnetic tunnel junctions (MTJs). A large TMC is observed at a low bias of 75 mV, which is suitable for low-power electronics. The fitting results between experimental data and calculation based on extended Debye–Fröhlich model reveal that the large TMC ratio is obtained owing to the high spin polarization of FeCo and the spin capacitance of the lattice-matched interface between FeCo and MgAl2O4. Based on this model, a TMC ratio could reach 1500% in MTJs with a spin polarization of 90%.

Recently, chirality-induced spin selectivity (CISS) has been observed in chiral molecules and has become attractive for applications in magnetoresistance (MR) devices. In this study, we fabricate CISS-based organic spin valves (OSVs) consisting of the chiral molecule 1,1′-Bi-2-naphthol (BINOL), sandwiched between an Au electrode and Co/Pt layers with perpendicular magnetic anisotropy, with and without an AlOx layer. We successfully fabricated Au/R-(+)-BINOL/Co/Pt/Co/Pt/Cr (Au/R-(+)-BINOL/[Co/Pt]2) and Au/S-(−)-BINOL/[Co/Pt]2 OSVs. These devices, which exhibit sharp interfaces, demonstrate clear CISS-based MR effects under a low magnetic field of ∼20 mT at room temperature. The MR curves of both Au/R-(+)-BINOL/[Co/Pt]2 and Au/S-(−)-BINOL/[Co/Pt]2 OSVs correspond well to the perpendicular magnetization curves of the [Co/Pt]2 electrodes. The polarity of the resistance change also exhibits opposite behaviors in the two devices. This indicates that an MR effect based on CISS is successfully observed in the Au/BINOL/[Co/Pt]2 OSVs. In addition, we fabricate Au/BINOL/AlOx/[Co/Pt]2 OSVs, in which an AlOx layer is inserted. We find that inserting an AlOx layer at the molecule/Co interface decreases both the MR and signal-to-noise (S/N) ratios of the MR curves compared with those of devices without an AlOx layer. The results of this study can contribute to elucidating the mechanism of CISS and provide new insights into its effect for spintronic device applications.

We have successfully observed the chirality-induced spin selectivity (CISS)-based magnetoresistance (MR) effect in Au/N-(3S)-3,7-dimethyloctyl[1]benzothieno[3,2-b]benzothiophene-2-carboxyamide (S-BTBT-CONHR)/Ni78Fe22 nanodevices at room temperature.

Emergent inductance has attracted significant interest for its relevance in both interesting fundamental physics and practical applications in magnetic devices that demand miniaturization without compromising inductance. In this Letter, we report the discovery of a stepwise magnetic field-induced emergent magneto-inductance (EML) effect in Permalloy (Py) thin films deposited on polycarbonate (PC) substrates. Remarkably, Py/PC devices exhibit an exceptionally large inductance variation exceeding 1 μH at room temperature, and intriguingly, a sign reversal of inductance occurs around the zero magnetic field. The dependencies of the EML effect on frequency, step magnetic field changes, and film width can be explained from the theory based on the spin motive force driven by transient domain wall motion. This study opens up exciting avenues for advancing our understanding of emergent inductance in fundamental physics and paves the way for practical applications in flexible magnetic devices.

Abstract Magnetocapacitance (MC) effect has been observed in systems where both symmetries of time-reversal and space-inversion are broken, for examples, in multiferroic materials and spintronic devices. The effect has received increasing attention due to its interesting physics and the prospect of applications. Recently, a large tunnel magnetocapacitance (TMC) of 332% at room temperature was reported using MgO-based (001)-textured magnetic tunnel junctions (MTJs). Here, we report further enhancement in TMC beyond 420% at room temperature using epitaxial MTJs with an MgAl2O4(001) barrier with a cation-disordered spinel structure. This large TMC is partially caused by the high effective tunneling spin polarization, resulted from the excellent lattice matching between the Fe electrodes and the MgAl2O4 barrier. The epitaxial nature of this MTJ system sports an enhanced spin-dependent coherent tunneling effect. Among other factors leading to the large TMC are the appearance of the spin capacitance, the large barrier height, and the suppression of spin flipping through the MgAl2O4 barrier. We explain the observed TMC by the Debye-Fröhlich modelled calculation incorporating Zhang-sigmoid formula, parabolic barrier approximation, and spin-dependent drift diffusion model. Furthermore, we predict a 1000% TMC in MTJs with a spin polarization of 0.8. These experimental and theoretical findings provide a deeper understanding on the intrinsic mechanism of the TMC effect. New applications based on large TMC may become possible in spintronics, such as multi-value memories, spin logic devices, magnetic sensors, and neuromorphic computing.