Rashba-like Spin Textures in Graphene Promoted by Ferromagnet-Mediated Electronic Hybridization with a Heavy Metal.

Epitaxial graphene/ferromagnetic metal (Gr/FM) heterostructures deposited onto heavy metals have been proposed for the realization of spintronic devices because of their perpendicular magnetic anisotropy and sizable Dzyaloshinskii-Moriya interaction (DMI), allowing for both enhanced thermal stability and stabilization of chiral spin textures. However, establishing routes toward this goal requires the fundamental understanding of the microscopic origin of their unusual properties. Here, we elucidate the nature of the induced spin-orbit coupling (SOC) at Gr/Co interfaces on Ir.

Observation by SANS and PNR of pure Néel-type domain wall profiles and skyrmion suppression below room temperature in magnetic [Pt/CoFeB/Ru] multilayers.

We report investigations of the magnetic textures in periodic multilayers [Pt(1 nm)/(CoFeB(0.8 nm)/Ru(1.4 nm)] using polarised neutron reflectometry (PNR) and small-angle neutron scattering (SANS).

Large Interfacial Rashba Interaction Generating Strong Spin-Orbit Torques in Atomically Thin Metallic Heterostructures.

The hallmark of spintronics has been the ability of spin-orbit interactions to convert a charge current into a spin current and vice versa, mainly in the bulk of heavy metal thin films. Here, we demonstrate how a light metal interface profoundly affects both the nature of spin-orbit torques and its efficiency in terms of damping-like () and field-like () effective fields in ultrathin Co films. We measure unexpectedly / ratios much larger than 1 by inserting a nanometer-thin Al metallic layer in Pt|Co|Al|Pt as compared to a similar stacking, including Cu as a reference.

Probing of three-dimensional spin textures in multilayers by field dependent X-ray resonant magnetic scattering.

In multilayers of magnetic thin films with perpendicular anisotropy, domain walls can take on hybrid configurations in the vertical direction which minimize the domain wall energy, with Néel walls in the top or bottom layers and Bloch walls in some central layers. These types of textures are theoretically predicted, but their observation has remained challenging until recently, with only a few techniques capable of realizing a three dimensional characterization of their magnetization distribution. Here we perform a field dependent X-ray resonant magnetic scattering measurements on magnetic multilayers exploiting circular dichroism contrast to investigate such structures.

Ultrafast time-evolution of chiral Néel magnetic domain walls probed by circular dichroism in x-ray resonant magnetic scattering.

Non-collinear spin textures in ferromagnetic ultrathin films are attracting a renewed interest fueled by possible fine engineering of several magnetic interactions, notably the interfacial Dzyaloshinskii-Moriya interaction. This allows for the stabilization of complex chiral spin textures such as chiral magnetic domain walls (DWs), spin spirals, and magnetic skyrmions among others. We report here on the behavior of chiral DWs at ultrashort timescale after optical pumping in perpendicularly magnetized asymmetric multilayers.

Tuning the Magnetic Anisotropy of Lanthanides on a Metal Substrate by Metal-Organic Coordination.

Taming the magnetic anisotropy of lanthanides through coordination environments is crucial to take advantage of the lanthanides properties in thermally robust nanomaterials. In this work, the electronic and magnetic properties of Dy-carboxylate metal-organic networks on Cu(111) based on an eightfold coordination between Dy and ditopic linkers are inspected. This surface science study based on scanning probe microscopy and X-ray magnetic circular dichroism, complemented with density functional theory and multiplet calculations, reveals that the magnetic anisotropy landscape of the system is complex.

Thermoelectric Signature of Individual Skyrmions.

We experimentally study the thermoelectrical signature of individual skyrmions in chiral Pt/Co/Ru multilayers. Using a combination of controlled nucleation, single skyrmion annihilation, and magnetic field dependent measurements the thermoelectric signature of individual skyrmions is characterized. The observed signature is explained by the anomalous Nernst effect of the skyrmion's spin structure.

Imaging non-collinear antiferromagnetic textures via single spin relaxometry.

Antiferromagnetic materials are promising platforms for next-generation spintronics owing to their fast dynamics and high robustness against parasitic magnetic fields. However, nanoscale imaging of the magnetic order in such materials with zero net magnetization remains a major experimental challenge. Here we show that non-collinear antiferromagnetic spin textures can be imaged by probing the magnetic noise they locally produce via thermal populations of magnons.

Controlled Individual Skyrmion Nucleation at Artificial Defects Formed by Ion Irradiation.

Magnetic skyrmions are particle-like deformations in a magnetic texture. They have great potential as information carriers in spintronic devices because of their interesting topological properties and favorable motion under spin currents. A new method of nucleating skyrmions at nanoscale defect sites, created in a controlled manner with focused ion beam irradiation, in polycrystalline magnetic multilayer samples with an interfacial Dzyaloshinskii-Moriya interaction, is reported.

Thermally Activated Processes for Ferromagnet Intercalation in Graphene-Heavy Metal Interfaces.

The development of graphene (Gr) spintronics requires the ability to engineer epitaxial Gr heterostructures with interfaces of high quality, in which the intrinsic properties of Gr are modified through proximity with a ferromagnet to allow for efficient room temperature spin manipulation or the stabilization of new magnetic textures. These heterostructures can be prepared in a controlled way by intercalation through graphene of different metals. Using photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), we achieve a nanoscale control of thermally activated intercalation of a homogeneous ferromagnetic (FM) layer underneath epitaxial Gr grown onto (111)-oriented heavy metal (HM) buffers deposited, in turn, onto insulating oxide surfaces.

Room-temperature stabilization of antiferromagnetic skyrmions in synthetic antiferromagnets.

Room-temperature skyrmions in ferromagnetic films and multilayers show promise for encoding information bits in new computing technologies. Despite recent progress, ferromagnetic order generates dipolar fields that prevent ultrasmall skyrmion sizes, and allows a transverse deflection of moving skyrmions that hinders their efficient manipulation. Antiferromagnetic skyrmions shall lift these limitations.

Unraveling Dzyaloshinskii-Moriya Interaction and Chiral Nature of Graphene/Cobalt Interface.

A major challenge for future spintronics is to develop suitable spin transport channels with long spin lifetime and propagation length. Graphene can meet these requirements, even at room temperature. On the other side, taking advantage of the fast motion of chiral textures, that is, Néel-type domain walls and magnetic skyrmions, can satisfy the demands for high-density data storage, low power consumption, and high processing speed.

Emergence of the Stoner-Wohlfarth astroid in thin films at dynamic regime.

The Stoner-Wohlfarth (SW) model is the simplest model that describes adequately the magnetization reversal of nanoscale systems that are small enough to contain single magnetic domains. However for larger sizes where multi-domain effects are present, e.g.

Direct observation of temperature-driven magnetic symmetry transitions by vectorial resolved MOKE magnetometry.

Angle- and temperature-dependent vectorial magnetometry measurements are necessary to disentangle the effective magnetic symmetry in magnetic nanostructures. Here we present a detailed study on an Fe(1 0 0) thin film system with competing collinear biaxial (four-fold symmetry) and uniaxial (two-fold) magnetic anisotropies, carried out with our recently developed full angular/broad temperature range/vectorial-resolved magneto-optical Kerr effect magnetometer, named TRISTAN. The data give direct views on the angular and temperature dependence of the magnetization reversal pathways, from which characteristic axes, remanences, critical fields, domain wall types, and effective magnetic symmetry are obtained.