Magnetoresistance is the tendency of a material to change the value of its electrical resistance in an externally-applied magnetic field. There are a variety of effects that can be called magnetoresistance. Some occur in bulk non-magnetic metals and semiconductors, such as geometrical magnetoresistance, Shubnikov–de Haas oscillations, or the common positive magnetoresistance in metals. Other effects occur in magnetic metals, such as negative magnetoresistance in ferromagnets or anisotropic magnetoresistance (AMR). Finally, in multicomponent or multilayer systems, giant magnetoresistance (GMR), tunnel magnetoresistance (TMR), colossal magnetoresistance (CMR), and extraordinary magnetoresistance (EMR) can be observed.
Spintronics, also known as spin electronics, is the study of the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid-state devices. The field of spintronics concerns spin-charge coupling in metallic systems; the analogous effects in insulators fall into the field of multiferroics.
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins pointing in opposite directions. This is, like ferromagnetism and ferrimagnetism, a manifestation of ordered magnetism. The phenomenon of antiferromagnetism was first introduced by Lev Landau in 1933.
Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to remove moisture.
Magnetoresistive random-access memory (MRAM) is a type of non-volatile random-access memory which stores data in magnetic domains. Developed in the mid-1980s, proponents have argued that magnetoresistive RAM will eventually surpass competing technologies to become a dominant or even universal memory. Currently, memory technologies in use such as flash RAM and DRAM have practical advantages that have so far kept MRAM in a niche role in the market.
Tunnel magnetoresistance (TMR) is a magnetoresistive effect that occurs in a magnetic tunnel junction (MTJ), which is a component consisting of two ferromagnets separated by a thin insulator. If the insulating layer is thin enough, electrons can tunnel from one ferromagnet into the other. Since this process is forbidden in classical physics, the tunnel magnetoresistance is a strictly quantum mechanical phenomenon, and lies in the study of spintronics.
Colossal magnetoresistance (CMR) is a property of some materials, mostly manganese-based perovskite oxides, that enables them to dramatically change their electrical resistance in the presence of a magnetic field. The magnetoresistance of conventional materials enables changes in resistance of up to 5%, but materials featuring CMR may demonstrate resistance changes by orders of magnitude.
Giant magnetoresistance (GMR) is a quantum mechanical magnetoresistance effect observed in multilayers composed of alternating ferromagnetic and non-magnetic conductive layers. The 2007 Nobel Prize in Physics was awarded to Albert Fert and Peter Grünberg for the discovery of GMR, which also sets the foundation for the study of spintronics.
Stuart Stephen Papworth Parkin is an experimental physicist, Managing Director at the Max Planck Institute of Microstructure Physics in Halle and an Alexander von Humboldt Professor at the Institute of Physics of the Martin-Luther-University Halle-Wittenberg.
Spin-polarized scanning tunneling microscopy (SP-STM) is a type of scanning tunneling microscope (STM) that can provide detailed information of magnetic phenomena on the single-atom scale additional to the atomic topography gained with STM. SP-STM opened a novel approach to static and dynamic magnetic processes as precise investigations of domain walls in ferromagnetic and antiferromagnetic systems, as well as thermal and current-induced switching of nanomagnetic particles.
Gallium manganese arsenide, chemical formula (Ga,Mn)As is a magnetic semiconductor. It is based on the world's second most commonly used semiconductor, gallium arsenide,, and readily compatible with existing semiconductor technologies. Differently from other dilute magnetic semiconductors, such as the majority of those based on II-VI semiconductors, it is not paramagnetic but ferromagnetic, and hence exhibits hysteretic magnetization behavior. This memory effect is of importance for the creation of persistent devices. In (Ga,Mn)As, the manganese atoms provide a magnetic moment, and each also acts as an acceptor, making it a p-type material. The presence of carriers allows the material to be used for spin-polarized currents. In contrast, many other ferromagnetic magnetic semiconductors are strongly insulating and so do not possess free carriers. (Ga,Mn)As is therefore a candidate material for spintronic devices but it is likely to remain only a testbed for basic research as its Curie temperature could only be raised up to approximately 200 K.
Spinmechatronics is neologism referring to an emerging field of research concerned with the exploitation of spin-dependent phenomena and established spintronic methodologies and technologies in conjunction with electro-mechanical, magno-mechanical, acousto-mechanical and opto-mechanical systems. Most especially, spinmechatronics concerns the integration of micro- and nano- mechatronic systems with spin physics and spintronics.
Spin engineering describes the control and manipulation of quantum spin systems to develop devices and materials. This includes the use of the spin degrees of freedom as a probe for spin based phenomena. Because of the basic importance of quantum spin for physical and chemical processes, spin engineering is relevant for a wide range of scientific and technological applications. Current examples range from Bose–Einstein condensation to spin-based data storage and reading in state-of-the-art hard disk drives, as well as from powerful analytical tools like nuclear magnetic resonance spectroscopy and electron paramagnetic resonance spectroscopy to the development of magnetic molecules as qubits and magnetic nanoparticles. In addition, spin engineering exploits the functionality of spin to design materials with novel properties as well as to provide a better understanding and advanced applications of conventional material systems. Many chemical reactions are devised to create bulk materials or single molecules with well defined spin properties, such as a single-molecule magnet. The aim of this article is to provide an outline of fields of research and development where the focus is on the properties and applications of quantum spin.
Everspin Technologies, Inc. is a publicly traded semiconductor company headquartered in Chandler, Arizona, United States. It develops and manufactures discrete magnetoresistive RAM or magnetoresistive random-access memory (MRAM) products, including Toggle MRAM and Spin-Transfer Torque MRAM (STT-MRAM) product families. It also licenses its technology for use in embedded MRAM (eMRAM) applications, magnetic sensor applications as well as performs backend foundry services for eMRAM.
Bruce Alvin Gurney was an American physicist responsible for pioneering advances in magnetic recording. In particular, he was central to the development of the giant magnetoresistance (GMR) sensors first used in hard disk drives in 1997.
Spinterface is a term coined to indicate an interface between a ferromagnet and an organic semiconductor. This is a widely investigated topic in molecular spintronics, since the role of interfaces plays a huge part in the functioning of a device. In particular, spinterfaces are widely studied in the scientific community because of their hybrid organic/inorganic composition. In fact, the hybridization between the metal and the organic material can be controlled by acting on the molecules, which are more responsive to electrical and optical stimuli than metals. This gives rise to the possibility of efficiently tuning the magnetic properties of the interface at the atomic scale.
Mohindar Singh Seehra is an Indian-American Physicist, academic and researcher. He is Eberly Distinguished Professor Emeritus at West Virginia University (WVU).
Gang Cao is an American condensed matter physicist, academic, author, and researcher. He is a professor of physics at the University of Colorado Boulder. and Director of Center for Experiments on Quantum Materials.
Robert Hilton Meservey was an American physicist, specializing in condensed matter physics. He is known as the co-discoverer, with Paul Tedrow, of spin-polarized tunneling, which enabled the development of spin polarized scanning tunneling microscopy and other applications.
Bernard Dieny is a research scientist and an entrepreneur. He is Chief Scientist at SPINTEC, a CEA/CNRS/UGA research laboratory that he co-founded in 2002 in Grenoble, France. He is also co-founder of two startup companies: Crocus Technology on MRAM and magnetic sensors in 2006 and EVADERIS on circuits design in 2014.
