Research / Technical - Page 10

Researchers in Germany, led by the Max Born Institute, have developed a novel technique to obtain “in depth” and time-resolved view on magnetization, employing broadband femtosecond soft X-ray pulses to study the transient evolution of magnetization depth profiles within a magnetic thin film system. This is vital as the future development of functional magnetic devices based on ultrafast optical manipulation of spins requires an understanding of the depth-dependent spin dynamics across the interfaces of complex magnetic heterostructures.

In current information technology, functional magnetic devices typically consist of stacks of thin layers of magnetic and nonmagnetic materials, each only about one nanometer thick. The stacking, choice of atomic species, and the resulting interfaces between the layers are key to the particular function, for example as realized in the giant magnetoresistance read heads in all magnetic hard drives. Over the last years, it was shown that ultrashort laser pulses down to the femtosecond range (1 femtosecond = 10-15 s) can effectively and very fast manipulate the magnetization in a material, allowing a transient change or even permanent reversal of the magnetization state. While these effects have been predominantly studied in simple model systems, future applications will require an understanding of magnetization dynamics in more complex structures with nanometer-scale heterogeneity.

Researchers at Cornell University and University of Nebraska have discovered a strategy to switch the magnetization in thin layers of a ferromagnet. This a technique has the potential to lead to the development of more energy-efficient magnetic memory devices.

Scientists have been trying for many years to change the orientation of electron spins in magnetic materials by manipulating them with magnetic fields. But researchers including Dan Ralph, the F.R. Newman Professor of Physics in the College of Arts and Sciences and the paper's senior author, have instead looked to using spin currents carried by electrons, which exist when electrons have spins generally oriented in one direction.

A team of scientists, led by City College of New York physicist Lia Krusin-Elbaum, has designed a technique that uses ionic hydrogen to reduce charge carrier density in the bulk of three-dimensional (3D) topological insulators and magnets. The result is that robust non-dissipative surface or edge quantum conduction channels can be accessed for manipulation and control.

This approach could open the door to new quantum device platforms for harnessing emergent topological states for nano-spintronics and fault-tolerant quantum computing.

Researchers at Johns Hopkins University, University of Texas at Austin, Northeastern University and Argonne National Laboratory have reported a new quantum phenomenon in antiferromagnetic insulators that could open the door to new ways of powering  spintronic devices.

Antiferromagnetic insulators are advantageous in spintronic applications because of their low stray fields and rapid magnetic dynamics. Controlling their magnetization and reading their magnetic state is critical for these applications, but they are challenging.

Researchers at Columbia University, Brookhaven National Laboratory, University of Washington, Oak Ridge National Laboratory and the National Institute for Materials Science in Japan have found a strong link between electron transport and magnetism in a material called chromium sulfide bromide (CrSBr).

Created in the lab of Columbia University chemist Xavier Roy, CrSBr is a van der Waals crystal that can be peeled back into stackable 2D layers that are just a few atoms thin. In contrast to related materials that are rapidly destroyed by oxygen and water, CrSBr crystals are stable at ambient conditions. These crystals also maintain magnetic properties at a relatively high temperature of -280 F, obviating the need for expensive liquid helium cooled to -450 F.

Scientists from MPI CPfS, in collaboration with colleagues from National Yang Ming Chiao Tung University, National Cheng Kung University, and National Synchrotron Radiation Research Center in Taiwan as well as from Hiroshima University in Japan, have used strained engineering on multiferroic BiFeO₃ (BFO) thin films, to fabricate bistable antiferromagnetic states at room temperature for the first time.

These two antiferromagnetic states are non-volatile and very close to each other in energy, which was verified by soft x-ray linear dichroism spectroscopy. Moreover, these two non-volatile antiferromagnetic states can be reversibly switched by a moderate magnetic field and a non-contact optical approach. The team stressed that the conductivity of the two antiferromagnetic domains is drastically different.

A team of scientists from the Institut national de la recherche scientifique (INRS), in collaboration with TU Wien, Austria, the French national synchrotron facility (SOLEIL) and other international partners, has reported a breakthrough in understanding how spin evolves in extremely short time scales - one millionth of one billionth of a second.

So far, studies on the subject strongly relied on limited access large X-ray facilities such as free-electron lasers and synchrotrons. The team demonstrates, for the first time, a tabletop ultrafast soft X-ray microscope to spatio-temporally resolve the spin dynamics inside rare earth materials, which are promising for spintronic devices.

An international team that included scientists from Japan's RIKEN and the Australian National University have shown that Water waves can be used to visualize fundamental concepts, such as spin angular momentum, that arise in relativistic field theory. This could help to provide new insights into different wave systems.

The spin of an electron is usually described as the electron spinning on its axis, similar to a spinning top. However, this is a simplistic explanation and a fuller description of spin is more abstract. Now, Konstantin Bliokh of the RIKEN Theoretical Quantum Physics Laboratory and his team have shown that spin can appear as small circular motions of water particles in water waves.

University of Nebraska-Lincoln's scientist Christian Binek and University at Buffalo's Jonathan Bird and Keke He have teamed up to develop the first magneto-electric transistor.

Along with curbing the energy consumption of any microelectronics that incorporate it, the team's design could reduce the number of transistors needed to store certain data by as much as 75%, said Nebraska physicist Peter Dowben, leading to smaller devices. It could also lend those microelectronics steel-trap memory that remembers exactly where its users leave off, even after being shut down or abruptly losing power.

A team of researchers from Ames Laboratory and Iowa State University, as well as collaborators from the United States, Germany, and the United Kingdom, have reported on new Fermi arcs that can be controlled through magnetism and could be the future of electronics based on electron spins.

During the team's investigation of the rare-earth monopnictide NdBi (neodymium-bismuth), thet discovered a new type of Fermi arc that appeared at low temperatures when the material became antiferromagnetic, i.e., neighboring spins point in opposite directions. Fermi surfaces in metals are a boundary between energy states that are occupied and unoccupied by electrons. Fermi surfaces are normally closed contours forming shapes such as spheres, ovoids, etc. Electrons at the Fermi surface control many properties of materials such as electrical and thermal conductivity, optical properties, etc. In extremely rare occasions, the Fermi surface contains disconnected segments that are known as Fermi arcs and often are associated with exotic states like superconductivity.