Vacuum Resonance States as Atomic-Scale Probes of Noncollinear Surface Magnetism.

The reflection of electrons at noncollinear magnetic surfaces is investigated by spin-polarized scanning tunneling microscopy and spectroscopy on unoccupied resonance states located in vacuo. Even for energies up to 20 eV above the Fermi level, the resonance states are found to be spin split, exhibiting the same local spin quantization axis as the underlying spin texture. Mapping the spin-dependent electron phase shift upon reflection at the surface on the atomic scale demonstrates the relevance of all magnetic ground state interactions for the scattering of spin-polarized low-energy electrons.

Magneto-Seebeck tunneling on the atomic scale.

The tunneling of spin-polarized electrons across a magnetic tunnel junction driven by a temperature gradient is a fundamental process for the thermal control of electron spin transport. We experimentally investigated the atomic-scale details of this magneto-Seebeck tunneling by placing a magnetic probe tip in close proximity to a magnetic sample at cryogenic temperature, with a vacuum as the tunneling barrier. Heating the tip and measuring the thermopower of the junction while scanning across the spin texture of the sample lead to spin-resolved Seebeck coefficients that can be mapped at atomic-scale lateral resolution.

Magnetic Nano-skyrmion Lattice Observed in a Si-Wafer-Based Multilayer System.

Growth, electronic properties, and magnetic properties of an Fe monolayer (ML) on an Ir/YSZ/Si(111) multilayer system have been studied using spin-polarized scanning tunneling microscopy. Our experiments reveal a magnetic nano-skyrmion lattice, which is fully equivalent to the magnetic ground state that has previously been observed for the Fe ML on Ir(111) bulk single crystals. In addition, the experiments indicate that the interface-stabilized skyrmion lattice is robust against local atomic lattice distortions induced by multilayer preparation.

Individual atomic-scale magnets interacting with spin-polarized field-emitted electrons.

We resonantly inject spin-polarized field-emitted electrons in thermally switching nanomagnets. A detailed lifetime analysis as a function of the spin-polarized emission current reveals that considerable Joule heating is generated, and spin-transfer torque results in a directed switching. A trend of higher switching efficiency per electron is observed with an increasing emission current, probably due to the excitation of Stoner modes.