Spatially Resolved Spin-Injection Probability for Gallium Arsenide

Radical Single-Molecule Junctions

Radicals are unique molecular systems for applications in electronic devices due to their open-shell electronic structures. Radicals can function as good electrical conductors and switches in molecular circuits while also holding great promise in the field of molecular spintronics. However, it is both challenging to create stable, persistent radicals and to understand their properties in molecular junctions. The goal of this Perspective is to address this dual challenge by providing design principles for the synthesis of stable radicals relevant to molecular junctions, as well as offering current insight into the electronic properties of radicals in single-molecule devices. By exploring both the chemical and physical properties of established radical systems, we will facilitate increased exploration and development of radical-based molecular systems.

Atomic-Scale Photon Mapping Revealing Spin-Current Relaxation

A nanoscopic understanding of spin-current dynamics is crucial for controlling the spin transport in materials. However, gaining access to spin-current dynamics at an atomic scale is challenging. Therefore, we developed spin-polarized scanning tunneling luminescence spectroscopy (SP STLS) to visualize the spin relaxation strength depending on spin injection positions. Atomically resolved SP STLS mapping of gallium arsenide demonstrated a stronger spin relaxation in gallium atomic rows. Hence, SP STLS paves the way for visualizing spin current with single-atom precision.

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the interfaces between the different materials and defects that are common to real devices. Knowledge of these factors is especially important for the relatively new field of organic spintronics, where there is a severe lack of suitable experimental techniques that can yield depth-resolved information about the spin polarization of charge carriers within buried layers of real devices. Here, we present a new depth-resolved technique for measuring the spin polarization of current-injected electrons in an organic spin valve and find the temperature dependence of the measured spin diffusion length is correlated with the device magnetoresistance.

Ultrahigh vacuum, variable temperature, dual scanning tunneling microscope system operating under high magnetic field

We present a dual scanning tunneling microscope (DSTM) system operating between 2.2 K and room temperature, in a split-coil superconducting magnetic field up to 12 T and in ultrahigh vacuum. The DSTM consists of two compact STMs, each having x, y, and z coarse positioning piezoelectric steppers with embedded capacitive positioning sensor for navigation. Each STM can be operated independently and can achieve atomic resolution. The DSTM and the sample is configured in a way that allows the magnetic field orientation to be varied continuously from normal to parallel to the sample surface. Together with the sample, the DSTM can form a nanometer scale three terminal setup for transport measurement.

First-principles study of ferromagnetism in epitaxial Si-Mn thin films on Si(001)

Density-functional theory calculations are employed to investigate both the epitaxial growth and the magnetic properties of thin Mn and MnSi films on Si(001). For single Mn adatoms, we find a preference for the second-layer interstitial site. While a monolayer Mn film is energetically unfavorable, a capping-Si layer significantly enhances the thermodynamic stability and induces a change from antiferromagnetic to ferromagnetic order. For higher Mn coverage, a sandwiched Si-Mn thin film (with CsCl-like crystal structure) is found to be the most stable epitaxial structure. We attribute the strong ferromagnetic intralayer coupling in these films to Mn 3d-Si 3s3p exchange.

Advances in magnetic microscopy

A remarkable number of methods for direct, real-space imaging in magnetic microscopy have been demonstrated over the past decade and a half, and the pace of development shows no sign of slowing. Our understanding of magnetism increases as each striking new image of surface and thin-film magnetization is obtained. The continued development of high-performance magnetic information technologies also requires detailed study of the magnetostatics and dynamics of microscopic magnetic structures. Both fundamental curiosity and practical interest now drive us toward innovations in magnetic microscopy for nanometer-length scale and femtosecond temporal resolutions, which are beyond the limits of traditional imaging techniques. This survey is intended to provide an overview of the motivations, accomplishments, and future prospects for this discipline.

Spintronics: a spin-based electronics vision for the future

This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

Paramagnetic ion-doped nanocrystal as a voltage-controlled spin filter

A theory of spin injection from a ferromagnetic source into a semiconductor through a paramagnetic ion-doped nanocrystal is developed. Spin-polarized current from the source polarizes the ion; the polarized ion, in turn, controls the spin polarization of the current flowing through the nanocrystal. Depending on voltage, the ion can either enhance the injection coefficient by several times or suppress it. Large ion spins produce stronger enhancement of spin injection.