Competition of Dzyaloshinskii-Moriya and higher-order exchange interactions in Rh/Fe atomic bilayers on Ir(111)

Using spin-polarized scanning tunneling microscopy and density functional theory we demonstrate the occurrence of a novel type of noncollinear spin structure in Rh/Fe atomic bilayers on Ir(111). We find that higher-order exchange interactions depend sensitively on the stacking sequence. For fcc-Rh/Fe/Ir(111) frustrated exchange interactions are dominant and lead to the formation of a spin spiral ground state with a period of about 1.5 nm. For hcp-Rh/Fe/Ir(111) higher-order exchange interactions favor a double-row wise antiferromagnetic or "uudd" state. However, the Dzyaloshinskii- Moriya interaction at the Fe/Ir interface leads to a small angle of about 4{\deg} between adjacent magnetic moments resulting in a canted "uudd" ground state

Writing and Deleting Single Magnetic Skyrmions

Topologically nontrivial spin textures have recently been investigated for spintronic applications. Here, we report on an ultrathin magnetic film in which individual skyrmions can be written and deleted in a controlled fashion with local spin-polarized currents from a scanning tunneling microscope. An external magnetic field is used to tune the energy landscape, and the temperature is adjusted to prevent thermally activated switching between topologically distinct states. Switching rate and direction can then be controlled by the parameters used for current injection. The creation and annihilation of individual magnetic skyrmions demonstrates the potential for topological charge in future information-storage concepts

Writing and Deleting Single Magnetic Skyrmions

Topologically nontrivial spin textures have recently been investigated for spintronic applications. Here, we report on an ultrathin magnetic film in which individual skyrmions can be written and deleted in a controlled fashion with local spin-polarized currents from a scanning tunneling microscope. An external magnetic field is used to tune the energy landscape, and the temperature is adjusted to prevent thermally activated switching between topologically distinct states. Switching rate and direction can then be controlled by the parameters used for current injection. The creation and annihilation of individual magnetic skyrmions demonstrates the potential for topological charge in future information-storage concepts

Electrical detection of magnetic skyrmions by non-collinear magnetoresistance

Magnetic skyrmions are localised non-collinear spin textures with high potential for future spintronic applications. Skyrmion phases have been discovered in a number of materials and a focus of current research is the preparation, detection, and manipulation of individual skyrmions for an implementation in devices. Local experimental characterization of skyrmions has been performed by, e.g., Lorentz microscopy or atomic-scale tunnel magnetoresistance measurements using spin-polarised scanning tunneling microscopy. Here, we report on a drastic change of the differential tunnel conductance for magnetic skyrmions arising from their non-collinearity: mixing between the spin channels locally alters the electronic structure, making a skyrmion electronically distinct from its ferromagnetic environment. We propose this non-collinear magnetoresistance (NCMR) as a reliable all-electrical detection scheme for skyrmions with an easy implementation into device architectures

Nanoscale magnetic skyrmions and target states in confined geometries

Research on magnetic systems with broken inversion symmetry has been stimulated by the experimental proof of particlelike configurations known as skyrmions, whose nontrivial topological properties make them ideal candidates for spintronic technology. In this class of materials, Dzyaloshinskii-Moriya interactions (DMI) are present, which favor the stabilization of chiral configurations. Recent advances in material engineering have shown that in confined geometries it is possible to stabilize skyrmionic configurations at zero field. Moreover, it has been shown that in systems based on Pd/Fe bilayers on top of Ir(111) surfaces skyrmions can be as small as a few nanometres in diameter. In this work, we present scanning tunneling microscopy measurements of small Pd/Fe and Pd2/Fe islands on Ir(111) that exhibit a variety of different spin textures, which can be reproduced using discrete spin simulations. These configurations include skyrmions and skyrmionlike states with extra spin rotations such as the target state, which have been of interest due to their promising dynamic properties. Furthermore, using simulations we analyze the stability of these skyrmionic textures as a function of island size, applied field and boundary conditions of the system. An understanding of the parameters and conditions affecting the stability of these magnetic structures in confined geometries is crucial for the development of energetically efficient and optimally sized skyrmion-based devices.</p

Data set for: Nano-scale magnetic skyrmions and target states in confined geometries

This data set contains the libraries and scripts to completely reproduce the simulations of the publication "Nanoscale magnetic skyrmions and target states in confined geometries". These simulations are based on the Fidimag code [1] which can perform discrete spin simulations. The latest version of this data set can be found at: https://github.com/davidcortesortuno/paper-2019_nanoscale_skyrmions_target_states_confined_geometries [1] Bisotti, M.-A. et al., (2018). Fidimag – A Finite Difference Atomistic and Micromagnetic Simulation Package. Journal of Open Research Software. 6(1), p.22

Electrical detection of magnetic skyrmions by tunnelling non-collinear magnetoresistance

Magnetic skyrmions are localized non-collinear spin textures with a high potential for future spintronic applications(1-12). skyrmion phases have been discovered in a number of materials(9,11) and a focus of current research is to prepare, detect and manipulate individual skyrmions for implementation in devices(6-8). the local experimental characterization of skyrmions has been performed by, for example, lorentz microscopy(3) or atomic-scale tunnel magnetoresistance measurements using spin-polarized scanning tunnelling microscopy(4,7,12). here we report a drastic change of the differential tunnel conductance for magnetic skyrmions that arises from their non-collinearity: mixing between the spin channels locally alters the electronic structure, which makes a skyrmion electronically distinct from its ferromagnetic environment. we propose this tunnelling non-collinear magnetoresistance as a reliable all-electrical detection scheme for skyrmions with an easy implementation into device architectures