Ferromagnetism

Researchers from the University of Missouri and Oak Ridge National Laboratory have discovered a new type of quasiparticle found in all magnetic materials, no matter their strength or temperature. These new properties shake up what researchers previously knew about magnetism, showing it’s not as static as once believed.

“We’ve all seen the bubbles that form in sparkling water or other carbonated drink products,” said Ullrich, Curators’ Distinguished Professor of Physics and Astronomy. “The quasiparticles are like those bubbles, and we found they can freely move around at remarkably fast speeds”. This discovery could help the development of a new generation of electronics that are faster, smarter and more energy efficient. But first, scientists need to determine how this finding could work into those processes.

Researchers at King Abdullah University of Science and Technology (KAUST) and Khalifa University of Science and Technology have investigated the transmission, tunneling magnetoresistance ratio and spin injection efficiency of bilayer LaI₂ using a combination of first-principles calculations and the non-equilibrium Green’s function method. 

Multilayer graphene electrodes were used by the team, to build a magnetic tunnel junction with bilayer LaI₂ as ferromagnetic barrier. The magnetic tunnel junction reportedly proved to be a perfect spin filter device with an impressive tunneling magnetoresistance ratio of 653% under a bias of 0.1 V and a still excellent performance in a wide bias range. The team said that in combination with the obtained high spin injection efficiency, this could hold great potential from an application point of view.

Researchers at Osaka Metropolitan University, University of Nottingham, Czech Academy of Sciences, Diamond Light Source, ohannes Kepler University Linz, Johannes Gutenberg Universität Mainz, TU Wien and Masaryk University have used symmetry, ab initio theory, and experiments to explore x-ray magnetic circular dichroism (XMCD) in the altermagnetic class. The international research group recently pioneered a new method to identify altermagnets, using manganese telluride (α-MnTe) as a testbed. 

Magnetic materials have traditionally been classified as either ferromagnetic or antiferromagnetic. However, there appears to be a third class of magnetic materials exhibiting what is known as 'altermagnetism'. In ferromagnetic materials, all the electron spins point in the same direction, while in antiferromagnetic materials, the electron spins are aligned in opposite directions, half pointing one way and half the other, canceling out the net magnetism. Altermagnetic materials are proposed in theory to possess properties combining those of both antiferromagnetic and ferromagnetic materials. One potential application of altermagnetic materials is in spintronics technology, which aims to utilize the spin of electrons effectively in electronic devices such as next-generation magnetic memories. However, identifying altermagnets has been a challenge.

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.

Researchers from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), led by Associate Prof. Li Xingxing and Prof. Yang Jinlong, recently developed a novel chemical method for two-dimensional metal-organic lattices.

In spintronics, it is paramount to develop an efficient way to reversibly control the spin order of materials. Though various physical methods have been proposed, chemically achieving this has posed significant challenges. The researchers proposed the utilization of the well-recognized lactim−lactam tautomerization process to reversibly modulate the magnetic phase transition in two-dimensional (2D) organometallic lattices. This could offer new pathways for controlling the electrical and magnetic characteristics of materials.

Researchers at China's Hefei University of Technology, University of Science and Technology of China, South China University of Technology, Chinese Academy of Sciences (CAS), Anhui University, Australia's RMIT University, University of New South Wales, Saudi Arabia's Al-Baha University and University of Jeddah have reported magnetism in a quasi-2D magnet Cr_1.2Te₂, observed at room temperature (290 K). 

By intercalating protons into van der Waals ferromagnet Cr_1.2Te₂ nanoflakes, the group of researchers successfully induced a room-temperature magnetic phase transition from ferromagnetism to antiferromagnetism.

Scientists at Delft University of Technology have used superconducting diamagnetism to shape the magnetic environment governing the transport of spin waves—collective spin excitations in magnets that are promising on-chip signal carriers—in a thin-film magnet. 

The team has shown that it’s possible to control and manipulate spin waves on a chip using superconductors for the first time. These tiny waves in magnets may offer an alternative to electronics in the future, interesting for energy-efficient information technology or connecting pieces in a quantum computer, for example. The results of this work give scientists new insight into the interaction between magnets and superconductors.

A new study at BESSY II analyzes the formation of skyrmions in ferrimagnetic thin films of dysprosium and cobalt in real time and with high spatial resolution. This could be an important step towards characterizing suitable materials with skyrmions more precisely. 

Magnetic skyrmions are tiny vortices-like of magnetic spin textures that can, in principle, be used for spintronic devices. But currently it is still difficult to control and manipulate skyrmions at room temperature.

Researchers at North Carolina State University (NCSU) have reported a new distinct form of silicon called Q-silicon which, among other interesting properties, is ferromagnetic at room temperature. The team's recent findings could lead to advances in quantum computing, including the creation of a spin qubit quantum computer that is based on controlling the spin of an electron.

“The discovery of Q-silicon having robust room temperature ferromagnetism will open a new frontier in atomic-scale, spin-based devices and functional integration with nanoelectronics,” said Jay Narayan, the John C. Fan Family Distinguished Chair in Materials Science and corresponding author of the paper describing the work.

Researchers from the Chinese Academy of Sciences (CAS) and the University of Science and Technology of China have demonstrated considerable control of magnetism at low electric fields (E) at room temperature. The E-induced phase transformation and lattice distortion were found to lead to the E control of magnetism in multiferroic BiFeO₃-based solid solutions near the morphotropic phase boundary (MPB). 

Multiferroic materials, with magnetic and ferroelectric properties, are promising for multifunctional memory devices. Magnetoelectric-based control methods in insulating multiferroic materials require less energy and have potential for high-speed, low-power information storage applications. BiFeO₃ is a room-temperature multiferroic material with potential for use in spintronics devices, but its weak ferromagnetic and magnetoelectric effects and high voltage required for manipulation are weaknesses. In their recent study, the researchers grew single crystals of the multiferroic 0.58BiFeO₃-0.42Bi_0.5K_0.5TiO₃ (BF-BKT), which lies in the tetragonal region adjacent to the MPB.