Iron is the most useful magnet in our daily life. It is a ‘ferromagnet’ at room temperature and ambient pressure, but displays a variety of other magnetic properties that depend on its crystallographic structure.
Now, using a technique called angle-resolved photoemission spectroscopy (ARPES) on iron thin films, Jun Miyawaki from the RIKEN SPring-8 Center, Harima, and colleagues have uncovered the origins of a particular type of magnetic order, called the spin spiral (SS), which has eluded understanding despite extensive experimental and theoretical efforts.
Magnetism in iron is associated with the spin, or quantum angular momentum, of the valence electrons of its atoms. In a ferromagnet the spins are parallel to each other; however, a structural change in the position of atoms in the crystal matrix of iron can order the spins into a spin spiral, such that the angle between the spins varies periodically.
Miyawaki says he was shocked when he realized that the electronic structure of SS-ordered iron was still an open question; it is fundamental to understanding the material’s behavior.
To elucidate the origin of this magneto-structural behavior, Miyawaki and colleagues studied ultrathin iron films consisting of eight monolayers with a ferromagnetic bilayer at the top and six SS-ordered monolayers below. The researchers used the ARPES technique to bombard the SS layers with soft x-ray photons and knock out electrons. Then they measured the intensities and angles of the emitted electrons. This yielded information about the electrons' energy and momenta from which they constructed Fermi surfaces to characterize and predict various properties of iron.
Crucially, the researchers successfully mapped the energy-momentum relationship for electrons moving in- and out-of-plane of the iron film separately. Miyawaki notes that this required a concerted effort to develop the necessary instrumentation by his team at RIKEN and a team at the Japan Synchrotron Radiation Research Institute (JASRI).
The experimental results showed stark differences with respect to the symmetries of the in-plane and out-of-plane Fermi surfaces. A detailed analysis revealed that the SS magnetic order is directly linked to electrons ‘inhabiting’ specific regions of the out-of-plane Fermi surface, thus providing direct information about its origin on a microscopic level.
These findings not only provide vital clues to theoretical studies, but also suggest that iron thin films may be used in spintronics devices based on the spin-transfer torque phenomenon, Miyawaki notes. “Because right- and left-handed spin spirals exert a different spin-transfer torque on spin-polarized electrons, iron thin films could serve as memory devices,” he says.
The corresponding author for this highlight is based at the Excitation Order Research Team, RIKEN SPring-8 Center
1. Miyawaki, J., Chainani, A., Takata, Y., Mulazzi, M., Oura, M., Senba, Y., Ohashi, H. & Shin, S. Out-of-plane nesting driven spin spiral in ultrathin Fe/Cu(001) films. Physical Review Letters 104, 066407 (2010)
gro-pr | Research asia research news
Astronomers release most complete ultraviolet-light survey of nearby galaxies
18.05.2018 | NASA/Goddard Space Flight Center
A quantum entanglement between two physically separated ultra-cold atomic clouds
17.05.2018 | University of the Basque Country
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology