Antiferromagnetism - Page 3

Researchers from North Carolina State University, University of North Carolina at Chapel Hill, Massachusetts Institute of Technology (MIT),  National Renewable Energy Laboratory, Duke University, Wayne State University and The Hong Kong University of Science and Technology have created a mixed magnon state in an organic hybrid perovskite material by utilizing the Dzyaloshinskii-Moriya-Interaction (DMI).

The resulting material has potential for processing and storing quantum computing information. The work also expands the number of potential materials that can be used to create hybrid magnonic systems.

Researchers from Tohoku University, University of California Riverside and Massachusetts Institute of Technology (MIT) have highlighted a series of critical achievements in antiferromagnetic spintronics (including their own contributions), revealing an emerging frontier distinguished by the coherent spin dynamics of antiferromagnets. 

Within antiferromagnetic spintronics, scientists have exerted a lot of efforts on the switching and readout of static magnetic order. But coherent spin dynamics, the key to exploring the wave features of spins and integrating spintronics with quantum and neuromorphic technologies, has only received attention very recently. "The coherent spin dynamics of antiferromagnets exhibits a lot more intriguing features than that of ferromagnets," says Jiahao Han, a JSPS Research Fellow working at the Research Institute of Electrical Communication (RIEC), Tohoku University. "By harnessing this unique property, the team has been pursuing breakthroughs that eventually form a new chapter named coherent antiferromagnetic spintronics."

A team led by researchers at the National Institute of Standards and Technology (NIST), the University of South Florida (USF), Harvey-Mudd College and the University of the District of Columbia has discovered a route toward reducing the sputter damage during growth of Nanolayered Pt/Co/Ir-based Synthetic Antiferromagnets that delivers significant improvements in perpendicular magnetic anisotropy and interlayer exchange coupling energy.

Synthetic antiferromagnets (SAFs) are a core component for top-pinned magnetic tunnel junction memory systems in semiconductor production. Establishing low-damage sputtering techniques to protect the multiple interfaces between sub-nm thick constituent layers delivers improved SAF properties could be key to data retention in high-density, sub-10 nm diameter magnetic memory arrays.

Researchers from Germany's Max Planck Institute of Microstructure Physics have reported a lift-off and transfer method to fabricate three-dimensional racetrack memories from freestanding magnetic heterostructures grown on a water-soluble sacrificial release layer.

The fabrication of three-dimensional nanostructures is key to the development of next-generation nanoelectronic devices with a low device footprint. Magnetic racetrack memories encode data in a series of magnetic domain walls that are moved by current pulses along magnetic nanowires. To date, most studies have focused on two-dimensional racetracks.

Researchers from Oak Ridge National Laboratory, Helmholtz-Zentrum Berlin (HZB) and University of Amsterdam have used inelastic neutron scattering and methods of integrability to experimentally observe and theoretically describe a local, coherent, long-lived, quasiperiodically oscillating magnetic state emerging out of the distillation of propagating excitations following a local quantum quench in a Heisenberg antiferromagnetic chain.

This “quantum wake” displays similarities to Floquet states, discrete time crystals and nonlinear Luttinger liquids. The team also showed how this technique reveals the non-commutativity of spin operators, and is thus a model-agnostic measure of a magnetic system’s “quantumness.”

A team of researchers, led by Igor Barsukov at the University of California, Riverside, in collaboration with researchers at Helmholtz-Zentrum Dresden-Rossendorf, the University of Utah, and the University of California, Irvine, has demonstrated efficient spin transport in an antiferromagnet/ferromagnet hybrid that remains robust up to room temperature. The researchers observed coupling of magnonic subsystems in the antiferromagnet and ferromagnet and recognized its importance in spin transport, a key process in the operation of spin-based devices. 

Antiferromagnets have zero net magnetization and are insensitive to external magnetic field perturbations. Antiferromagnetic spintronic devices hold great promise for creating future ultra-fast and energy-efficient information storage, processing, and transmission platforms, potentially leading to faster and more energy-efficient computers.  However, in order to be useful for applications impacting everyday life, the devices need to be able to operate at room temperature. One of the key factors in realizing antiferromagnetic spintronics is the injection of spin current at the antiferromagnetic interface. Previously, efficient spin injection at these interfaces was realized at cryogenic temperatures. 

Researchers from FLEET at Australia's RMIT University, South China University of Technology and the Chinese Academy of Sciences (CAS) have observed electric gate-controlled exchange-bias effect in van der Waals heterostructures. The team describes this as “a promising platform for future energy-efficient, beyond-CMOS electronics”.

The exchange-bias (EB) effect, which originates from interlayer magnetic coupling, has played a significant role in fundamental magnetics and spintronics since its discovery. Although manipulating the EB effect by an electronic gate has been a significant goal in spintronics, until now, only very limited electrically-tunable EB effects have been demonstrated.

Researchers from the University of Tokyo and CREST (Japan Science and Technology Agency) have explored the world of spintronics and other related areas of solid state physics with a focus on antiferromagnets. The team has reported, in its recent study, the experimental realization of perpendicular and full spin–orbit torque switching of an antiferromagnetic binary state.

The team used the chiral antiferromagnet Mn₃Sn, which exhibits the magnetization-free anomalous Hall effect owing to a ferroic order of a cluster magnetic octupole hosted in its chiral antiferromagnetic state. They fabricated heavy-metal/Mn₃Sn heterostructures by molecular beam epitaxy and introduce perpendicular magnetic anisotropy of the octupole using an epitaxial in-plane tensile strain. By using the anomalous Hall effect as the readout, the team demonstrated 100% switching of the perpendicular octupole polarization in a 30-nanometre-thick Mn₃Sn film with a small critical current density of less than 15 megaamperes per square centimeter. Their theory is that the perpendicular geometry between the polarization directions of current-induced spin accumulation and of the octupole persistently maximizes the spin–orbit torque efficiency during the deterministic bidirectional switching process. The team's recent work provides a significant basis for antiferromagnetic spintronics.

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.

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.