Tag: spin

Iron under the ARPES Lens: how spin and magnetism shape the metal’s surface state

Iron under the ARPES Lens: how spin and magnetism shape the metal’s surface state

Researchers from the Jerzy Haber Institute of Catalysis and Surface Chemistry of the Polish Academy of Sciences in Kraków have carried out advanced experiments using angle-resolved photoemission spectroscopy (ARPES). They discovered a new surface state of iron Fe(001), whose symmetry changes depending on the magnetization direction of the layer. The results of their study have been published in the prestigious New Journal of Physics.

The electronic band structure of iron has been investigated for decades, but earlier studies were limited by experimental constraints. Today, with access to high-resolution ARPES facilities, such as the Phelix beamline at the Solaris synchrotron in Kraków, scientists can explore the electronic states of materials with unprecedented precision.

For the first time, the existence of a surface state on Fe(001) was unambiguously demonstrated in the epitaxial Fe/Au(001) system. Moreover, the Kraków team was the first to map this state across the full range of energy and momentum. Previous experiments, for example on Fe(001)/W(001), had been restricted to only a few high-symmetry directions or normal emission. By examining the surface state throughout the Brillouin zone, the researchers identified specific regions where spin–orbit coupling modifies the surface electronic states depending on the magnetization direction.

Read more on the SOLARIS website

Image: Surface state of Fe(001)/Au(001) within entire Brillouin zone and Rashba effect at the zone boudary

Accoustic spin waves: towards a new paradigm of on-chip communication

Accoustic spin waves: towards a new paradigm of on-chip communication

For the first time researchers have observed directly sound-driven spin waves (magnetoacoustic waves) and have revealed its nature.

Results show that these magnetization waves can go up to longer distances (up to centimeters) and have larger amplitudes than the commonly known spin waves. The study, published in Phys. Rev. Lett., is carried out by researchers from the University of Barcelona (UB), the Institute of Materials Science of Barcelona (ICMAB-CSIC), and the ALBA Synchrotron, in collaboration with the Paul-Drude-Institut in Berlin.

Researchers have observed directly and for the first time magnetoacoustic waves (sound-driven spin waves), which are considered as potential information carriers for novel computation schemes. These waves have been generated and observed on hybrid magnetic/piezoelectric devices. The experiments were designed by a collaboration between the University of Barcelona (UB), the Institute of Materials Science of Barcelona (ICMAB-CSIC) and the ALBA Synchrotron. The results show that magnetoacoustic waves can travel over long distances -up to centimeters- and have larger amplitudes than expected.

>Read more on the ALBA website

Image: TOP: A propagating and a standing magnetization wave in ferromagnetic Nickel, driven by magnetoelastic coupling to a surface acoustic wave in a piezoelectric LiNbO3substrate. The images combine line profiles (color indicating the local magnetization direction) at different delay times between the probing X-ray pulse and the electrical SAW excitation.
BOTTOM: Scheme of the strain caused by the surface acoustic waves (SAWs) in the piezoelectric (in green color scale) and magnetic modulation in the ferromagnetic material (in orange-cyan color scale).

Control of magnetoresistance in spin valves

Control of magnetoresistance in spin valves

Molecules, due to their wide-ranging chemical functionalities that can be tailored on demand, are becoming increasingly attractive components for applications in materials science and solid-state physics. Remarkable progress has been made in the fields of molecular-based electronics and optoelectronics, with devices such as organic field-effect transistors and light emitting diodes. As for spintronics, a nascent field which aims to use the spin of the electron for information processing, molecules are proposed to be an efficient medium to host spin-polarized carriers, due to their weak spin relaxation mechanisms. While relatively long spin lifetimes are measured in molecular devices, the most promising route toward device functionalization is to use the chemical versatility of molecules to achieve a deterministic control and manipulation of the electron spin.

Spin-polarized hybrid states induced by the interaction of the first molecular monolayers on ferromagnetic substrates are expected to govern the spin polarization at the molecule–metal interface, leading to changes in the sign and magnitude of the magnetoresistance in spin-valve devices. The formation of spin-polarized hybrid states has been determined by spin-polarized spectroscopy methods and principle-proven in nanosized molecular junctions, but not yet verified and implemented in large area functional device architectures.

>Read more on the ALBA website

Image: Magnetoresistance (top) and X-ray spectroscopy (bottom) measurements, evidencing the control of the magnetoresistance sign and amplitude by engineering spin valves with NaDyClq/NiFe and NaDyClq/Co interfaces, and their corresponding interfacial molecule-metal hybridization states.