Magnetism - Page 3

A study by Brazilian physicist Aline Ramires with Jose Lado, a Spanish-born researcher at the Swiss Federal Institute of Technology (ETH Zurich), showed that a simple sheet of graphene has fascinating properties due to a quantum phenomenon in its electron structure called Dirac cones. The system becomes even more interesting if it comprises two superimposed graphene sheets, and one is very slightly turned in its own plane so that the holes in the two carbon lattices no longer completely coincide. For specific angles of twist, the bilayer graphene system displays exotic properties such as superconductivity.

The researchers found that the application of an electrical field to such a system produces an effect identical to that of an extremely intense magnetic field applied to two aligned graphene sheets. "I performed the analysis, and it was computationally verified by Lado," Ramires said. "It enables graphene's electronic properties to be controlled by means of electrical fields, generating artificial but effective magnetic fields with far greater magnitudes than those of the real magnetic fields that can be applied."

Researchers from the Regional Center of Advanced Technologies and Materials (RCPTM) at Palacký University in the Czech Republic, together with the colleagues from the Institute of Physics (FZU) of the Czech Academy of Science (CAS) and the Institute of Organic Chemistry and Biochemistry (IOCB) of the CAS, have designed a new way to control the electronic and magnetic properties of molecules.

Traditionally, such a change can be induced by application of external stimuli, such as light, temperature, pressure, and magnetic field. The Czech scientists have instead developed a way to use weak non-covalent interactions of molecules with the surface of chemically modified graphene.

Scientists from St. Petersburg University and Tomsk University in Russia, along with teams at the Max Planck Institute in Germany and University of the Basque Country, Spain, have modified graphene in such a way that it has taken the properties of cobalt and gold: magnetism and spinorbit interaction. This advance can greatly benefit quantum computers.

The graphene was (for the first time, according to the researchers) modified to adopt such fundamental properties as magnetism and spin-orbit interaction. The spin of an electron is a magnet induced by the spin of the electron around its axis. It also orbits the nucleus to produce electric current and therefore a magnetic field. The interaction between the magnet and magnetic field is a spin-orbit interaction. Unlike in gold, the spin-orbit interaction in graphene is extremely small. The interaction between graphene and gold increase spin-orbit interaction in graphene, while interaction between graphene and cobalt induces magnetism, the team explained.

Researchers from the Lawrence Berkeley National Laboratory discovered the world's first magnetic 2D material - chromium germanium telluride (CGT). It was debatable whether magnetism could survive in such thin materials - and this discovery could pave the way to extremely thin spintronics devices.

The CGT flakes were produced using the scotch-tape method - the same one used to produce graphene for the first time in Manchester in 2004.

Researchers at the Czech Republic created magnetized carbon by treating graphene layers with non-metallic elements, said to be the first non-metal magnet to maintain its magnetic properties at room temperature. The researchers say such magnetic graphene-based materials have potential applications in the fields of spintronics, biomedicine and electronics.

By treating graphene with other non-metallic elements such as fluorine, hydrogen, and oxygen, the scientists were able to create a new source of magnetic moments that communicate with each other even at room temperature. This discovery is seen as "a huge advancement in the capabilities of organic magnets".

A study at TIFR (Tata Institute of Fundamental Research) designed a system that allows electronic interactions to be observed in three layers of graphene. The study reveals a new kind of magnet and provides insight on how electronic devices using graphene could be made for fundamental studies as well as applications, shedding light on the magnetism of electrons in three layers of graphene at a low temperature of -272 Celsius that arises from the coordinated "whispers" between many electrons.

Metals have a large density of electrons, so being able to see the wave nature of electrons requires making metallic wires a few atoms wide. However, in graphene the density of electrons is much smaller and can be changed by making a transistor. As a result, the wave nature of electrons is easier to observe in graphene.

Saint Jean Carbon, a carbon science company engaged in the design and development of carbon materials and their applications, recently received (along with Western University) a grant from the The Natural Sciences and Engineering Research Council of Canada (NSERC) towards the development of graphene-based systems with special magnetic properties.

The $100,000 grant will be used to cover the cost of the lab work, testing, material creation and all research associated costs. The company stated that it aims to use the funds to get beyond the lab and into working prototypes, scaled models and future commercial production. In addition, SJC hopes that "the results will play a big role in the medical field as well in energy storage for electric cars and green energy creation".

Saint Jean Carbon, a carbon science company engaged in the exploration of natural graphite properties and related carbon products, has teamed up with the University of Western Ontario to create graphene that has a magnetic field (Magnetoresistance).

One of the involved researchers explained that: "Magnetoresistance (MR) refers to the significant change of electrical resistance of materials under a magnetic field. Magnetoresistance effects have been applied in magnetic sensors, spintronic devices and data storage. Magnetic sensors are extremely useful for today's industry for measurement and control purposes... This happens by detecting changes in electrical resistance brought on by the presence of a magnetic field. This is also known as magnetoresistance (MR). The market size of the magnetic sensor is increasing with annual growth rate at 10% because of new nanomaterials..."

Researchers at the Autonomous University of Madrid, in collaboration with CIC nanoGUNE and the Institut Néel of Grenoble, have demonstrated that the simple absorption of a hydrogen atom on a layer of graphene magnetizes a large region of it. As a result, by selectively manipulating these hydrogen atoms, it is possible to produce magnetic graphene with atomic precision.

Graphene inherently lacks magnetic properties. The hydrogen atom has the smallest magnetic moment (the magnitude that determines how much and in what direction a magnet will exert force). This work reveals how when a hydrogen atom touches a graphene layer it transfers its magnetic moment to it. The researchers explain that in contraposition to more common magnetic materials such as iron, nickel or cobalt, in which the magnetic moment generated by each atom is located within a few tenths of a nanometre, the magnetic moment induced in the graphene by each atom of hydrogen extends several nanometres, and likewise displays a modulation on an atomic scale.

Researchers at Joseph Fourier University in Grenoble, France, have found that coating a cobalt film in graphene could double the film's perpendicular magnetic anisotropy (PMA), so that it reaches a value 20 times higher than that of traditional metallic cobalt/platinum multilayers that are being researched for this property. In a material with a high PMA, the magnetization is oriented perpendicular to the interface of the material's layers. High-PMA materials are being researched for their applications in next-generation spintronic devices, such as high-density memories and heat-tolerant logic gates. 

A major goal in developing spintronic devices is to reduce the size of the devices while achieving long-term information retention of 10-plus years. In order to do this, the storage material must have a large PMA. Enhancement of effective PMA could be achieved either by increasing the surface PMA or by minimizing the saturation magnetization of the storage layer. These co-graphene heterostructures benefit from both these properties. The PMA enhancement in the graphene-coated cobalt films originates at the atomic level, where graphene affects the energy of cobalt's different electron orbitals. The graphene coating changes how these orbitals overlap with one another, which in turn changes the direction of the cobalt film's overall magnetic field: some of the magnetization that was originally parallel to the film surface is now oriented perpendicular to the film surface.