arXiv subjects

Diana C. Leitao

Publications and source records attributed to Diana C. Leitao.

3 recordsLinked to original sources

arXiv2026

Demonstration of on-chip all-optical switching of magnetization in integrated photonics

Ultrafast all-optical magnetization switching (AOS) holds great promise for nextgeneration spintronic memory and hybrid spintronic-photonic systems. However, most implementations to date rely on bulky free-space optical setups, limiting scalability and practical integration. As a critical step toward integrated applications, we demonstrate single-pulse AOS within a silicon nitride (Si3N4) photonic integrated circuit. Using trains of femtosecond laser pulses guided through on-chip waveguides, we achieve deterministic toggle switching in a sub-micron out-of-plane Co/Gd Hall cross patterned directly atop the photonic waveguide. Electrical readout via the anomalous Hall effect reveals a switching contrast of up to 90% for 500 nm-wide devices. In larger Hall crosses, the contrast decreases and switching becomes stochastic, consistent with spatially non-uniform optical absorption as confirmed by finite-element simulations. This behavior is hypothetically attributed to domain wall relaxation and thermally assisted (de)pinning processes within partially switched regions. Our results highlight the critical role of device scaling in achieving robust on-chip AOS and establish a foundation for ultrafast, energy-efficient, and fully integrated spintronic-photonic platforms.

physics.optics↗

arXiv2026

The Multi-Scale Dynamics of All-Optical Exchange Bias Reversal

Pinning magnetization in a ferromagnetic thin film is commonly realized through exchange biasing with an adjacent antiferromagnet. Field-cooling from above the Néel temperature is a reliable yet slow re-pinning method in exchange-biased systems. For on-demand reprogrammable devices, localized and rapid exchange bias repinning methods are essential. Recent work has shown that femtosecond laser pulses enable field-free reversal of exchange bias in tailored multilayer stacks. Contrary to field-cooling, our experiments with ultrafast excitation reach hitherto unexplored regimes in the exchange bias setting process. Here, we unravel these observations by considering both ultrafast magnetization dynamics on the femto- to picosecond timescale and slow heat-driven dynamics on millisecond timescales and upwards. We develop a microscopic framework of exchange bias setting in a polycrystalline antiferromagnetic thin film like IrMn that provides a complete description of the observations in our present experiments and those found in literature. We expand the use of our model by identifying material platforms and stack designs that lead to optimized performance, aiding further development of optically reprogrammable devices.

cond-mat.mes-hall↗

arXiv2024

Understanding Field-Free Single-Shot Laser-Induced Reversal of Exchange Bias

Exchange bias is applied ubiquitously throughout the spintronics industry for pinning magnetic moment in an orientation robust against external magnetic field disturbances. Enabling efficient manipulation of the exchange-biased pinning direction is key to add or advance device functionality. Conventional methods for achieving this reorientation commonly require long heating times and assisting magnetic fields, thus limiting speed and versatility. Here, we demonstrate a field-free $180^\circ$ reorientation of perpendicular exchange bias in a thin film system integrating Co/Gd layers with IrMn. Single femtosecond laser pulses trigger a reversal of the pinning direction, while preserving the unidirectionality required for referencing. We formulate a theoretical microscopic framework involving a wide range of timescales that accurately reproduces the experimental outcomes. The understanding of the underlying mechanisms delivers guiding principles for designing reprogrammable spintronic devices.

cond-mat.mes-hall↗