Research / Technical

Researchers at Japan's National Institute for Materials Science have developed an improved type of microscope that can visualize key aspects of electron spin states in materials. The quantum mechanical property of electrons called spin is more complex than the spin of objects in our everyday world but is related to it as a measure of an electron’s angular momentum. The spin states of electrons can have a significant impact on the electronic and magnetic behavior of the materials they are part of.

The technology, developed by Koichiro Yaji and Shunsuke Tsuda, is known as imaging-type spin-resolved photoemission microscopy (iSPEM). It uses the interaction of light with the electrons in a material to detect the relative alignment of the electron spins. It is particularly focused on electron spin polarization – the extent to which electron spins are collectively aligned in a specific direction.

Researchers at MIT have tackled key obstacles to bringing 2D magnetic materials into practical use. The team designed a “van der Waals atomically layered heterostructure” device where a 2D van der Waals magnet, iron gallium telluride, is interfaced with another 2D material, tungsten ditelluride. The team shows that the magnet can be toggled between the 0 and 1 states simply by applying pulses of electrical current across their two-layer device. 

Use of magnetic materials to build computing devices like memories and processors has emerged as a promising avenue for creating “beyond-CMOS” computers, which would use far less energy compared to traditional computers. Magnetization switching in magnets can be used in computation the same way that a transistor switches from open or closed to represent the 0s and 1s of binary code. While much of the research along this direction has focused on using bulk magnetic materials, a new class of magnetic materials — called two-dimensional van der Waals magnets — provides superior properties that can improve the scalability and energy efficiency of magnetic devices to make them commercially viable.

Researchers from Johannes Gutenberg-University Mainz, ALBA Synchrotron Light Facility and Tohoku University have identified quasiparticles called merons in a synthetic antiferromagnet for the first time, which could lead to new concepts for spintronics devices.

The spintronics field is still rather nascent as research is ongoing. Recent research has focused on structures called skyrmions as potential building blocks. These structures are quasiparticles made up of numerous electron spins and can be thought of as two-dimensional whirls (or “spin textures”) within a material. Skyrmions exist in many magnetic materials, including cobalt–iron–silicon and the manganese–silicide thin films in which they were first discovered. They are attractive spintronics candidates because they are robust to external perturbations, making them particularly stable for storing and processing the information they contain. At just tens of nanometres across, they are also much smaller than the magnetic domains used to encode data in today’s disk drives, making them ideal for future data storage technologies such as “racetrack” memories. Like skyrmions, merons are made up of numerous individual spins. Unlike them, their stray magnetic fields are miniscule, which would facilitate ultrafast operations and even higher information storage densities within a device. Until now, however, merons have only been observed in natural antiferromagnets, where they have proved difficult to analyze and manipulate.

An international team, including researchers from CNRS, Université Paris-Saclay, Chinese Academy of Sciences, the University at Buffalo, University of Minnesota, State University of New York and others, recently used electrical pulses to manipulate magnetic information into a polarized light signal, which could revolutionize long-distance optical telecommunications.

The researchers applied an electrical pulse to transfer spin information from electrons to photons, the particles that make up light, allowing the information to be carried great distances at great speed. Their method meets three crucial criteria — operation at room temperature, no need of magnetic field and the ability for electrical control — and opens the door to a range of applications, including ultrafast communication and quantum technologies.

Researchers from Tohoku University and Toho University have demonstrated chirality switching by electric current pulses at room temperature in a thin-film MnAu₂ helimagnetic conductor. The team also succeeded in detecting the chirality at zero magnetic fields by means of simple transverse resistance measurement utilizing the spin Berry phase in a bilayer device composed of MnAu₂ and a spin Hall material Pt. These results may pave the way to helimagnet-based spintronics. 

Helimagnetic structures, in which the magnetic moments are spirally ordered, host an internal degree of freedom called chirality corresponding to the handedness of the helix. The chirality seems quite robust against disturbances and is therefore promising for next-generation magnetic memory. While the chirality control was recently achieved by the magnetic field sweep with the application of an electric current at low temperature in a conducting helimagnet, problems such as low working temperature and cumbersome control and detection methods have to be solved in practical applications.

Zhengzhou University researchers have synthesized a new material that combines graphene's remarkable properties with a strong response to magnetic fields. 

Graphene has a long spin lifetime and hyperfine interactions, making it potentially favorable for spintronics applications. Despite the recent discoveries of spin-containing graphene materials, graphene-based materials with room-temperature macroscopic ferromagnetism are extremely rare. In their recent study, room-temperature ferromagnetic amorphous graphene oxide (GO) was synthesized by introducing abundant oxygen-containing functional groups and C defects into single-layered graphene, followed by a self-assembly process under supercritical CO₂ (SC CO₂). 

Researchers at North Carolina State University, University of Illinois at Urbana-Champaign, Duke University and Sivananthan Laboratories have relied on a printable organic polymer, that assembles into chiral structures when printed, to reliably measure the amount of charge produced in spin-to-charge conversion within a spintronic material at room temperature. 

The polymer’s tunable qualities and versatility make it desirable not only for less expensive, environmentally friendly, printable electronic applications, but also for use in understanding chirality and spin interactions more generally.

Researchers from Tohoku University have developed a theoretical model for high-performance spin wave reservoir computing (RC) that utilizes spintronics technology. This achievement could push scientists closer to realizing energy-efficient, nanoscale computing with unparalleled computational power.

Scientists are constantly striving to create neuromorphic devices that mimic the brain's processing capabilities, low power consumption, and its ability to adapt to neural networks. The development of neuromorphic computing is revolutionary, allowing scientists to explore nanoscale realms, GHz speed, with low energy consumption. In recent years, many advances in computational models inspired by the brain have been made. These artificial neural networks have demonstrated extraordinary performances in various tasks. However, current technologies are software-based; their computational speed, size, and energy consumption remain constrained by the properties of conventional electric computers.

Researchers at Newcastle University, National University of Singapore (NUS) and Japan's National Institute for Materials Science have reported a significant discovery in the field of spintronics based on the unique properties of an ultrathin, two-dimensional material called black phosphorus and how it transports spinning electrons.

Spintronics utilizes the intrinsic spin of electrons to create more energy-efficient devices. Electrons have a spin state of “up” or “down” causing the electrons to act like tiny magnets and manipulating this state has been seen by researchers as crucial for achieving lower power operation in electronic devices. This is because the spin motion of electrons inherently dissipates far less heat than the movement of electrical charge used in traditional electronics. Whilst the phenomenon of spin itself has been widely studied, the challenge has been finding a material with the optimal properties for creating the channels that transport spins.

Researchers have conducted experiments at the Swiss Light Source SLS that resulted in proof of the existence of a new type of magnetism: altermagnetism. The experimental discovery of this new branch of magnetism could signify new fundamental physics, with major implications for spintronics.

Since the discovery of antiferromagnets nearly a century ago, the family of magnetic materials has been divided into two fundamental phases: the ferromagnetic branch known for several millennia and the antiferromagnetic branch. The experimental proof of a third branch of magnetism, termed altermagnetism, was made by an international collaboration led by the Czech Academy of Sciences together with Paul Scherrer Institute PSI. The fundamental magnetic phases are defined by the specific spontaneous arrangements of magnetic moments—or electron spins—and of atoms that carry the moments in crystals.