Elmer Monteblanco | Searcharxiv

arXiv2025

Reversible magneto ionics in crystallized W Co20Fe60B20 MgO HfO2 ultra-thin films with perpendicular magnetic anisotropy

We have investigated electric field (E-field) induced modulation of perpendicular magnetic anisotropy (PMA) in both amorphous and crystalline W/CoFeB/MgO/HfO2 ultra-thin films. We find that in the amorphous state, the E-field effect is volatile and reversible, which is consistent with the conventional electrostatic effect through charge accumulation and depletion. In the crystallized system annealed at 370{\deg}C, we find that two effects are at play, a non-volatile and reversible voltage-induced effect on PMA and an electrostatic response. We discuss these results in terms of higher oxygen mobility at the crystallized CoFeB-MgO interface, which induces a non-volatile magnetoionic response. Modulating PMA in crystallized CoFeB-MgO materials through ionic migration opens the path to integrating magneto-ionics in full magnetic tunnel junctions.

cond-mat.mtrl-sci↗

arXiv2022

Quantum advantage in a molecular spintronic engine that harvests thermal fluctuation energy

Recent theory and experiments have showcased how to harness quantum mechanics to assemble heat/information engines with efficiencies that surpass the classical Carnot limit. So far, this has required atomic engines that are driven by cumbersome external electromagnetic sources. Here, using molecular spintronics, we propose an implementation that is both electronic and autonomous. Our spintronic quantum engine heuristically deploys several known quantum assets by having a chain of spin qubits formed by the paramagnetic Co centers of phthalocyanine (Pc) molecules electronically interact with electron-spin selecting Fe/C60 interfaces. Density functional calculations reveal that transport fluctuations across the interface can stabilize spin coherence on the Co paramagnetic centers, which host spin flip processes. Across vertical molecular nanodevices, we measure enduring dc current generation, output power above room temperature, two quantum thermodynamical signatures of the engine's processes, and a record 89% spin polarization of current across the Fe/C60 interface. It is crucially this electron spin selection that forces, through demonic feedback and control, charge current to flow against the built-in potential barrier. Further research into spintronic quantum engines, insight into the quantum information processes within spintronic technologies, and retooling the spintronic-based information technology chain, could help accelerate the transition to clean energy.

cond-mat.mes-hall↗