arXiv subjects

Reinoud Lavrijsen

Publications and source records attributed to Reinoud Lavrijsen.

At least 19 recordsLinked to original sources

arXiv2026

Induced superconductivity in selective-area grown SnTe devices

Topological superconductors are of high interest for applications in topological quantum computation. The required topologically superconducting state can be engineered by proximityinducing superconductivity in a topological insulator. Here, we explore the induced superconductivity in selective-area grown nanowires of the topological crystalline insulator SnTe on a InP substrate, through TEM/EDX and low-temperature electronic transport studies. The observed superconducting behavior likely originates from indium in the substrate diffusing upwards into the SnTe nanowire, forming a thin layer of InxSn1-xTe at the interface between the nanowire and the substrate. InxSn1-xTe is intrinsically superconducting for indium concentrations above 2%, resulting in superconductivity within the heterostructure. Little-Parks oscillations are observed in loop-shaped nanowire networks in an out-of-plane magnetic field. The half-period shift indicative of a topological superconducting state is absent, which is explained by dominant trivial transport channels obscuring any topological signatures.

cond-mat.mes-hall↗

arXiv2026

Facilitating electrical and laser-induced skyrmion nucleation with a dipolar-field enhanced effective DMI

We demonstrate experimentally how the nucleation of skyrmions in an Ir, Co, and Pt based magnetic multilayer is affected by introducing a layer dependent sign for the Dzyaloshinskii-Moriya interaction (DMI). In one stack, the bottom half of the stack is given a positive DMI and the top half a negative DMI, and as a result, the in-plane component of the dipolar field is aligned parallel to the effective field of the DMI in every layer, enhancing the effective DMI. We show that this enhanced DMI facilitates the nucleation and stability of skyrmions using both current-driven and laser-induced skyrmion nucleation. In the devices with an enhanced effective DMI, the density of nucleated skyrmions is greater by up to a factor 20 and skyrmions can be observed in stronger magnetic fields - suggesting that their stability is also improved. These results show that skyrmion nucleation depends strongly on the magnitude of the effective DMI in a magnetic multilayer and that the dipolar field within such a multilayer presents an effective route towards controlling the effective DMI, and thereby, the nucleation of chiral magnetic textures.

cond-mat.mtrl-sci↗

arXiv2025

Current-Induced Modulation of Spin-Wave Propagation in a Y-Junction via Transverse Spin-Transfer Torque

We report the transverse control of spin-wave propagation in the configuration where the spin-wave wavevector k is perpendicular to the charge-current density J. Building on theoretical predictions of spin-wave refraction by nonuniform spin-polarized currents, and guided by micromagnetic simulations used to optimize the device geometry and current distribution, we experimentally explore a Y-shaped Permalloy structure in which a locally injected current perturbs the spin-wave dispersion. Measurements reveal current-dependent amplitude differences between the two output branches, providing initial experimental indications consistent with transverse, spin-transfer-torque-driven deflection. Although the magnitude of the effect is modest and accompanied by significant uncertainties, the observed trends qualitatively follow expectations from the simulations. These results demonstrate the feasibility of influencing spin-wave routing through local current injection and establish a proof-of-concept basis for current-controlled manipulation of spin-wave propagation in reconfigurable magnonic circuits.

cond-mat.mes-hall↗

arXiv2025

Controlling Spin-Waves by Inhomogeneous Spin-Transfer Torques

We investigate the interplay between spin currents and spin waves in nanofabricated Permalloy waveguides with geometrical constrictions. Using propagating spin-wave spectroscopy, micromagnetic simulations, and analytical modeling, we provide experimental evidence that spin-wave phase can be modulated by inhomogeneous spin-transfer torques generated by current-density gradients shaped by the constriction geometry. Narrower constrictions enhance these gradients and modify the internal field for Damon-Eshbach spin waves, resulting in pronounced changes in spin-wave group velocity and phase. To our knowledge, this constitutes the first demonstration of deterministic phase modulation via engineered nonuniform spin-transfer torques. Beyond enabling a scalable route to magnonic interferometry - a building block for spin-wave-based computing - our findings establish a platform to control spin-wave dynamics in spatially varying current landscapes, relevant for analogue-gravity experiments in condensed matter systems.

cond-mat.mes-hall↗

arXiv2025

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↗

arXiv2025

A refinement of the Lorentz local field expression with impact on the Clausius-Mossotti and Lorentz-Lorenz models

In the 19th century Mossotti and Clausius developed an expression linking the electrical permittivity of a dielectric to the product of molecular polarizability and number density. Lorenz and Lorentz later extended this framework to encompass the refractive index of the dielectric. These classical expressions have proven remarkably successful in describing how permittivity and refractive index vary with number density, under the assumption that molecular polarizability remains relatively constant. While these models have stood the test of time and continue to offer valuable insights, their derivation relies on an approximation of the local electric field within a spherical cavity that simulates the molecular environment, excluding the field generated by the molecule or molecules themselves. For regimes of higher number densities, such as those encountered in densified dielectrics, employing an exact solution for the local field becomes increasingly important. This refinement extends the applicability of the Clausius-Mossotti and Lorentz-Lorenz equations and leads to more accurate estimates of molecular polarizability in general.

physics.optics↗

arXiv2024

AFM Cantilever Magnetometry for Measuring Femto-Nm Torques Generated by Single Magnetic Particles for Cell Actuation

Particles with high anisotropy in their magnetic properties and shape are of increasing interest for mechanobiology, where transducing a remotely applied magnetic field vector to a local mechanical response is crucial. An outstanding challenge is quantifying the mechanical torque of a single nanoparticle, typically in the range of atto- to femto-Newton-meters (Nm). The magneto-mechanical torque manifests due to a misalignment of the external magnetic field vector with the built-in magnetic anisotropy axis, as opposed to a magnetic force, and complicates the measurement scheme. In this work, we developed a method using a commercially available Atomic Force Microscopy setup and cantilevers to quantify the torque generated by a single synthetic antiferromagnetic (SAF) nanoplatelet with high perpendicular magnetic anisotropy. Specifically, we measured 1.6$\pm$0.6$\cdot$10$^{-15}$ Nm torque while applying 373$\pm$5 mT field at 12$\pm$2 degrees to the built-in anisotropy axis exerted by a single circular SAF nanoplatelet with 1.88 $μ$m diameter and 72 nm thickness, naively translating to a $\approx$ 1.7 nN maximum force at the nanoplatelet apex. This measured torque and derived force of the SAF nanoplatelets is strong enough for most applications in mechanobiology; for example, it can be used to rupture (cancer) cell membranes. Moreover, SAF nanoplatelets open a route for easy tuning of the built-in magnetic anisotropy and size, reducing the torque and allowing for small mechanical stimuli for ion channel activation. This work presents a straightforward and widely applicable method for characterizing magnetic particles' mechanical transduction, which is applied to SAF nanoplatelets with a high PMA.

cond-mat.mes-hall↗

arXiv2024

Investigating the Interplay between Spin-Polarization and Magnetic Damping in $\mathrm{Co}_{x}\mathrm{Fe}_{80-x}\mathrm{B}_{20}$ for Magnonics Applications

For magnonics and spintronics applications, the spin polarization ($P$) of a transport current and the magnetic damping ($α$) play a crucial role, e.g. for magnetization dynamics and magnetization switching applications. In particular, $P$ in a glassy (amorphous) 3d transition ferromagnet such as CoFeB and $α$ are both strongly affected by $s-d$ scattering mechanisms. Hence, a correlation can be expected which is a priori difficult to predict. In this work, $P$ and $α$ are measured using current-induced Doppler shifts using propagating spin-wave spectroscopy and broadband ferromagnetic resonance techniques in blanket films and current-carrying $Co_{\rm x}Fe_{\rm {80-x}}B_{\rm 20}$ alloy microstrips. The measured $P$ ranges from 0.18 $\pm$ 0.05 to 0.39 $\pm$ 0.05 and $α$ ranges from $(4.0\pm 0.2)\cdot10^{-3}$ to $(9.7\pm 0.6)\cdot10^{-3}$. We find that for increasing $P$ a systematic drop in $α$ is observed, indicating an interplay between magnetic damping and the spin polarization of the transport current which suggests that interband scattering dominates in $Co_{\rm x}Fe_{\rm {80-x}}B_{\rm 20}$. Our results may guide future experiments, theory, and applications in advancing spintronics and metal magnonics.

physics.app-ph↗

arXiv2024

Integrated magneto-photonic non-volatile multi-bit memory

We present an integrated magneto-photonic device for all-optical switching of non-volatile multi-bit spintronic memory. The bits are based on stand-alone magneto-tunnel junctions which are perpendicularly magnetized with all-optically switchable free layers, coupled onto photonic crystal nanobeam cavities on an indium phosphide based platform. This device enables switching of the magnetization state of the bits by locally increasing the power absorption of light at resonance with the cavity. We design an add/drop network of cavities to grant random access to multiple bits via a wavelength-division multiplexing scheme. Based on a three-dimensional finite-difference time-domain method, we numerically illustrate a compact device capable of switching and accessing 8 bits in different cavities with a 5 nm wavelength spacing in the conventional (C) telecommunication band. Our multi-bit device holds promise as a new paradigm for developing an ultrafast photonically-addressable spintronic memory and may also empower novel opportunities for photonically-driven spintronic-based neuromorphic computing.

physics.optics↗

arXiv2024

Picosecond all-optical switching of Co/Gd based synthetic ferrimagnets

Single pulse all-optical switching of magnetization (AOS) in Co/Gd based synthetic ferrimagnets carries promises for hybrid spintronic-photonic integration. A crucial next step progressing towards this vision is to gain insight into AOS and multi-domain state (MDS) behavior using longer pulses, which is compatible with state-of-the-art integrated photonics. In this work, we present our studies on the AOS and MDS of [Co/Gd]n (n = 1, 2) using ps optical pulses across a large composition range. We theoretically and experimentally show that a large Gd layer thickness can enhance the AOS energy efficiency and maximum pulse duration. We have identified two augmenting roles of Gd in extending the maximum pulse duration. On the inter-atomic level, we found that more Gd offers a prolonged angular momentum supply to Co. On the micromagnetic level, a higher Gd content brings the system to be closer to magnetic compensation in the equilibrized hot state, thereby reducing the driving force for thermally assisted nucleation of domain walls, combating the formation of a MDS. Our study presents a composition overview of AOS in [Co/Gd]n and offers useful physical insights regarding AOS fundamentals as well as the projected photonic integration.

cond-mat.mes-hall↗

arXiv2024

Interlayer Dzyaloshinskii-Moriya interaction in synthetic ferrimagnets

The antisymmetric interlayer exchange interaction, i.e., interlayer Dzyaloshinskii-Moriya interaction (IL-DMI) has attracted significant interest since this long-range chiral spin interaction provides a new dimension for controlling spin textures and dynamics. However, the role of IL-DMI in the field induced and spin-orbit torque (SOT) induced switching of synthetic ferrimagnets (SFi) has not been uncovered. Here, we exploit interlayer chiral exchange bias fields in SFi to address both the sign and magnitude of the IL-DMI. Depending on the degree of imbalance between the two magnetic moments of the SFi, the amount of asymmetry, addressed via loop shifts of the hysteresis loops under an in-plane field reveals a unidirectional and chiral nature of the IL-DMI. The devices are then tested with SOT switching experiments and the process is examined via both transient state and steady state detection. In addition to field-free SOT switching, we find that the combination of IL-DMI and SOT give rise to multi-resistance states, which provides a possible direction for the future design of neuromorphic computing devices based on SOT. This work is a step towards characterizing and understanding the IL-DMI for spintronic applications.

physics.app-ph↗

arXiv2024

Understanding voltage-controlled magnetic anisotropy effect for the manipulation of dipolar-dominated propagating spin waves

Spin waves, known for their ability to propagate without the involvement of moving charges, hold immense promise for on-chip information transfer and processing, offering a path toward post-CMOS computing technologies. This study investigates the potential synergy between propagating Damon-Eshbach spin waves and voltage-controlled magnetization in the pursuit of environmentally sustainable computing solutions. Employing micromagnetic simulations, we assess the feasibility of utilizing spin waves in DE mode in conjunction with localized voltage-induced alterations in surface anisotropy to enable low-energy logic operations. Our findings underscore the critical importance of selecting an optimal excitation frequency and gate width, which significantly influence the efficiency of the phase shift induced in propagating spin waves. Notably, we demonstrate that a realistic phase shift of 2.5$\left[ π\ \text{mrad}\right]$ can be achieved at a Co(5nm)/MgO material system via the VCMA effect. Moreover, by tuning the excitation frequency, Co layer thickness, gate width, and the use of a GdO\textsubscript{x} dielectric, we illustrate the potential to enhance the phase shift by a factor of 200 when compared to MgO dielectrics. This research contributes valuable insights towards developing next-generation computing technologies with reduced energy consumption.

physics.app-ph↗

arXiv2023

Ultrafast single-pulse all-optical switching in synthetic ferrimagnetic Tb/Co/Gd multilayers

In this work, we investigate single-shot all-optical switching (AOS) in Tb/Co/Gd/Co/Tb multilayers in an attempt to establish AOS in synthetic ferrimagnets with high perpendicular magnetic anisotropy. In particular, we study the effect of varying Tb thicknesses to disentangle the role of the two rare earth elements. Even though the role of magnetic compensation has been considered to be crucial, we find that the threshold fluence for switching is largely independent of the Tb content. Moreover, we identify the timescale for the magnetization to cross zero to be within the first ps after laser excitation using time-resolved MOKE. We conclude that the switching is governed mostly by interactions between Co and Gd.

cond-mat.mes-hall↗

arXiv2023

Ultralow power and shifting-discretized magnetic racetrack memory device driven by chirality switching and spin current

Magnetic racetrack memory has significantly evolved and developed since its first experimental verification and is considered as one of the most promising candidates for future high-density on-chip solid state memory. However, the lack of a fast and precise magnetic domain wall (DW) shifting mechanism and the required extremely high DW motion (DWM) driving current both make the racetrack difficult to commercialize. Here, we propose a method for coherent DWM that is free from above issues, which is driven by chirality switching (CS) and an ultralow spin-orbit-torque (SOT) current. The CS, as the driving force of DWM, is achieved by the sign change of DM interaction which is further induced by a ferroelectric switching voltage. The SOT is used to break the symmetry when the magnetic moment is rotated to the Bloch direction. We numerically investigate the underlying principle and the effect of key parameters on the DWM through micromagnetic simulations. Under the CS mechanism, a fast (102 m/s), ultralow energy (5 attojoule), and precisely discretized DWM can be achieved. Considering that skyrmions with topological protection and smaller size are also promising for future racetrack, we similarly evaluate the feasibility of applying such a CS mechanism to a skyrmion. However, we find that the CS only causes it to "breathe" instead of moving. Our results demonstrate that the CS strategy is suitable for future DW racetrack memory with ultralow power consumption and discretized DWM.

cond-mat.mes-hall↗

arXiv2023

Strain effects on magnetic compensation and spin reorientation transition of Co/Gd synthetic ferrimagnets

Synthetic ferrimagnets are an attractive materials class for spintronics as they provide access to all-optical switching of magnetization and, at the same time, allow for ultrafast domain wall motion at angular momentum compensation. In this work, we systematically study the effects of strain on the perpendicular magnetic anisotropy and magnetization compensation of Co/Gd and Co/Gd/Co/Gd synthetic ferrimagnets. Firstly, the spin reorientation transition of a bilayer system is investigated in wedge type samples, where we report an increase in the perpendicular magnetic anisotropy in the presence of in-plane strain. Using a model for magnetostatics and spin reorientation transition in this type of system, we confirm that the observed changes in anisotropy field are mainly due to the Co magnetoelastic anisotropy. Secondly, the magnetization compensation of a quadlayer is studied. We find that magnetization compensation of this synthetic ferrimagnetic system is not altered by external strain. This confirms the resilience of this material system against strain that may be induced during the integration process, making Co/Gd ferrimagnets suitable candidates for spintronics applications.

cond-mat.mtrl-sci↗

arXiv2023

Controlling magnetic skyrmion nucleation with Ga+ ion irradiation

In this paper, we show that magnetic skyrmion nucleation can be controlled using Ga+ ion irradiation, which manipulates the magnetic interface effects (in particular the magnetic anisotropy and Dzyaloshinskii-Moriya interaction) that govern the stability and energy cost of skyrmions in thin film systems. We systematically and quantitatively investigated what effect these changes have on the nucleation of magnetic skyrmions. Our results indicate that the energy cost of skyrmion nucleation can be reduced up to 26% in the studied dose range and that it scales approximately linearly with the square root of the domain-wall energy density. Moreover, the total number of nucleated skyrmions in irradiated devices after nucleation was found to depend linearly on the ion dose and could be doubled compared to nonirradiated devices. These results show that ion irradiation cannot only be used to enable local nucleation of skyrmions, but that it also allows for fine control of the threshold and efficiency of the nucleation process.

cond-mat.mes-hall↗

arXiv2022

Strongly nonlinear antiferromagnetic dynamics in high magnetic fields

Antiferromagnetic (AFM) materials possess a well-recognized potential for ultrafast data processing thanks to their intrinsic ultrafast spin dynamics, absence of stray fields, and large spin transport effects. The very same properties, however, make their manipulation difficult, requiring frequencies in THz range and magnetic fields of tens of Teslas. Switching of AFM order implies going into the nonlinear regime, a largely unexplored territory. Here we use THz light from a free electron laser to drive antiferromagnetic NiO into a highly nonlinear regime and steer it out of nonlinearity with magnetic field from a 33-Tesla Bitter magnet. This demonstration of large-amplitude dynamics represents a crucial step towards ultrafast resonant switching of AFM order.

cond-mat.mtrl-sci↗

arXiv2022

Design of an integrated hybrid plasmonic-photonic device for all-optical switching and reading of spintronic memory

We introduce a novel integrated hybrid plasmonic-photonic device for all-optical switching and reading of nanoscale ferrimagnet bits. The racetrack memory made of synthetic ferrimagnetic material with a perpendicular magnetic anisotropy is coupled on to a photonic waveguide onto the indium phosphide membrane on silicon platform. The device which is composed of a double V-shaped gold plasmonic nanoantenna coupled with a photonic crystal cavity can enable switching and reading of the magnetization state in nanoscale magnetic bits by enhancing the absorbed energy density and polar magneto-optical Kerr effect (PMOKE) locally beyond the diffraction limit. Using a three-dimensional finite-difference time-domain method, we numerically show that our device can switch and read the magnetization state in targeted bits down to ~100 nm in the presence of oppositely magnetized background regions in the racetrack with widths of 30 to 120 nm, clearly outperforming a bare photonic waveguide. Our hybrid device tackles the challenges of nonlinear absorption in the waveguide, weak PMOKE, and size mismatch between spintronics and integrated photonics. Thus, it provides missing link between the integrated photonics and nanoscale spintronics, expediting the development of ultrafast and energy efficient advanced on-chip applications.

physics.optics↗