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Magnetic and Spintronic Materials and Their Applications
Published in Song Sun, Wei Tan, Su-Huai Wei, Emergent Micro- and Nanomaterials for Optical, Infrared, and Terahertz Applications, 2023
Magnetic resistance. Magnetoresistance (MR) refers to the effect that the resistance changes when a magnetic field is applied. There are a variety of magnetoresistance effect, mainly including anisotropic magnetoresistance (AMR) [22], giant magnetoresistance (GMR) [2,3], tunnel magnetoresistance (TMR) [4], and colossal magnetoresistance (CMR) [23]. The AMR is an effect in single ferromagnetic or ferrimagnetic metals that the resistivity depends on the relative angle between the magnetization direction and the electric current direction. The GMR is a phenomenon that occurs in multilayered structures with ferromagnetic metallic layers separated by a non-magnetic metallic spacer, in which the resistance is low (or high) when the ferromagnetic metals are parallel- (or antiparallel-) magnetized. The TMR occurs in magnetic tunnel junction consists of two ferromagnetic layers separated by a thin insulator spacer; if a voltage is applied to the junction, electrons tunnel through the insulator space and the tunneling current (meanwhile the resistance) changes dramatically when the relative magnetization of the two ferromagnetic layers changes their alignment by magnetic field. Colossal magnetoresistance is an effect that occurs mostly in Mn-based perovskite oxides, which arises from the paramagnetic insulator-ferromagnetic metal phase transition under application of a magnetic field.
Magnetic Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Figure 7.7 illustrates the configuration that exhibits switchable TMR (Cockburn 2004). A fixed ferromagnet plate is separated from a free ferromagnet plate by a very thin (e.g., ≤1.5 nm thick film) insulating barrier. The magnitude of the tunneling current through the barrier is proportional to the product of the densities of spin-aligned electron quantum states in the conduction sub-band of the plates on either side of the barrier. If the magnetizations (and hence the majority electron spins) in the two plates are parallel, then the majority-spin-aligned electrons in the two plates tunnel more readily across the tunneling barrier. If the magnetizations (and hence majority electron spins) in the two plates are antiparallel, then the majority-spin-aligned electrons in one plate are inhibited from tunneling to the other plate (and vice versa) because the spin-aligned electron states are in minority there. Tunneling magnetoresistance: (a) antiparallel and (b) parallel spins.
Emerging Trends in Nanoscale Semiconductor Devices
Published in Suman Lata Tripathi, Sobhit Saxena, Sushanta Kumar Mohapatra, Advanced VLSI Design and Testability Issues, 2020
B. Vandana, B. S. Patro, J. K. Das, Sushanta Kumar Mohapatra, Suman Lata Tripathi
There are many devices developed to perform similar functions as that of transistors. The spin valve is one of them. It was first invented by Dieny et al. in 1991. This revolutionizes the industries that deal with storage devices and magnetic sensors. In a similar way, giant magnetoresistance (GMR)–based and tunneling magnetoresistance (TMR)–based devices are working. IBM, Honeywell, Freescale, SanDisk, and so on are some of the companies that are consistently marketing and improvising the technology associated with these types of devices. Magnetic tunnel junction and ferroelectric tunnel junction are also some of the most important spintronic devices that are used for logic and memory-based applications.
Electromagnetic field and artificial intelligence based fault detection and classification system for the transmission lines in smart grid
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Chetan Khadse, Abhijeet A. Patharkar, Bharat S. Chaudhari
Magnetic field sensors based on magnetoresistance (MR) effect can be used to carry out measurement of magnetic fields. The use of these sensors ensures the safety for maintenance. These can be placed away from the electrical equipment and can be pull apart easily. These sensors can detect the disturbance or change occurred in the magnetic field rather than the sensing physical quantity (Huang et al. 2019). While using magnetic field sensors there are chances of interference. External interference to electromagnetic sensors or the interference between multiple electromagnetic sensors can be avoided by using magnetic shielding enclosure. These magnetic shielding enclosures are made up of diamagnetic materials. This enclosure will helpful for avoiding interference [23]. The detailed mathematical model for current to magnetic field transformation and changes in magnetic fields is described and discussed as below subsections.
Room temperature magnetoimpedance of La0.67Sr0.33–xPbxMnO3 (x = 0–0.33) manganites
Published in Phase Transitions, 2019
Perovskite Manganites have been a subject of multidisciplinary research since last few years in the areas of solid–state physics, chemistry, materials science, etc. They exhibit a dramatic change in resistivity in presence of an external magnetic field, known as the colossal magnetoresistance (CMR) effect. But at room temperature under a low magnetic field, the CMR materials show a small value of dc magnetoresistance (MR) which restricts the practical applications of these materials. Hence, many recent investigations have been focused on their ac MR and magnetoimpedance (MI).