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Heusler Compound: A Novel Material for Optoelectronic, Thermoelectric, and Spintronic Applications
Published in Niladri Pratap Maity, Reshmi Maity, Srimanta Baishya, High-K Gate Dielectric Materials, 2020
The spin-based electronics that manipulate the electron spin degree of freedom is termed as spintronic, where the spin of an electron is tuned by an applied magnetic field that orients the spin for polarization. These polarized electrons are used to control the electric current. The ultimate goal is to develop a device that utilizes the spin of an electron. Once the spin functionality is added, it will provide significant versatility to future electronic products. Magnetic spin properties of electrons are used in many applications such as giant magnetoresistance (GMR), tunneling magnetoresistance (TMR) (Mathon et al., 2001; Ikeda et al., 2008), magnetic memory (MRAM) (Sbiaa et al., 2011; Bhatti et al., 2017) etc. Materials that undergo phase transition from semiconductor to ferromagnetic above room temperature are potential for a new generation of spintronic devices with enhanced electrical and optical properties. The field of spintronic revolutionized the digital world at post discovery of GMR effect (Baibich et al., 1988; Fert, 2005), and this discovery was the Nobel Prize winning work. The GMR effect occurs due to alignment of the spin of electrons with the applied magnetic field that includes the variation in the resistance of a material. A schematic component of spintronic is presented in Figure 9.11.
Magnetic Particle Biosensors
Published in Jeffrey N. Anker, O. Thompson Mefford, Biomedical Applications of Magnetic Particles, 2020
Yunzi Li, Paivo Kinnunen, Alexander Hrin, Mark A. Burns, Raoul Kopelman
Giant magnetoresistance (GMR) is the first of the anisotropic magnetic resistance (AMR) phenomena we will explore. GMR is one of the more common methods of detecting magnetic particle labels in biosensors. Essentially, the observed phenomenon of GMR is a measurable change in the resistance of a material when a small magnetic field is applied. For GMR sensors, the change in resistance due to a fairly small number of particles is detectable, and the effect increases with the number of magnetic particles resting on the sensor. The idea for the setup of a GMR biosensor is to attach a binding ligand to the substrate directly above the GMR sensors, and another binding ligand to the magnetic particles. When the target is present, it binds the magnetic particles to the substrate in an amount proportional to the amount of target. Finally, the presence of those magnetic particles results in a detectable change in the resistance of the GMR sensor, a change proportional to the amount of particles attached to the surface. Figure 9.7 shows fabricated GMR sensors and the essential process for how the GMR phenomenon can be used to detect the presence of biological agents.
Nanoscale Magnetism
Published in Klaus D. Sattler, 21st Century Nanoscience – A Handbook, 2020
Roopali Kukreja, Hendrik Ohldag
GMR was independently discovered by Albert Fert [19] and Peter Grünberg [33] in 1988, for which they were jointly awarded 2007 Nobel Prize in Physics. The basic idea of GMR effect is that the resistance of two ferromagnetic layers decoupled by a spacer layer (typically Cu or Au) is dependent upon their relative magnetic alignment. This structure is called a spin valve device. If both the layers are aligned parallel to each other, then the resistance is lower compared to the case when they are aligned antiparallel to each other. The difference in resistance of up to 110% has been observed between two configurations [32,33]. A few years later after the discovery of GMR, every hard disk drive was using this effect to ‘read’ orientation of magnetic bits which are used to store data. GMR effect is also used in biosensors, microelectromechanical systems and magnetoresistive random-access memory (MRAM) applications.
Magnetoresistance sensor-based rotor fault detection in induction motor using non-decimated wavelet and streaming data
Published in Automatika, 2022
S. Kavitha, N. S. Bhuvaneswari, R. Senthilkumar, N. R. Shanker
In this paper, anti-clockwise outward magnetic field analyses are performed with minimal components for hardware such as GMR sensor and Wifi-DAQ. The emitted outward magnetism of IM is absorbed by the GMR sensor. The GMR sensor has high signal sensitivity and high-temperature stability. It is small in dimension compared with existing sensors such as search coil, piezo electric, acceleration, and Hall effect sensor. Therefore, the GMR sensor should be placed in an optimized location for attaining good sensitivity. The optimized placement of the GMR sensor in IM is shown in Figure 2. The sensor is focussed on the stator outer region in D/2 cm distance and acquires an outward magnetic field with good sensitivity and minimum transverse field radiation. The magnetic spectrum is acquired by the GMR sensor and wirelessly transmitted to the personal computer through a Wi-Fi DAQ card. The GMR sensor signal received through the Wi-Fi DAQ card is recorded by the data acquisition software (SIGVIEW) and saved as a Microsoft Sound file (*.wav). This dot wav format of the outward magnetic signal of IM is analysed by non-hybrid and hybrid wavelet transforms, and the rotor condition is monitored through anti-clockwise magnetic flux outward spectrum signals from wavelet transform coefficients.
Heusler alloys for spintronic devices: review on recent development and future perspectives
Published in Science and Technology of Advanced Materials, 2021
Kelvin Elphick, William Frost, Marjan Samiepour, Takahide Kubota, Koki Takanashi, Hiroaki Sukegawa, Seiji Mitani, Atsufumi Hirohata
Spintronics has been initiated by the discovery of giant magnetoresistance (GMR) by Fert et al. [1] and Grünberg et al. [2] independently. A GMR device consists of a sandwich structure of a ferromagnet (FM)/non-magnet (NM)/FM multilayer, where an external magnetic field can align the FM magnetisations in parallel to achieve a low-resistance state as compared with a high-resistance state with antiparallel magnetisations without a field application. The first-generation spintronic devices are based on magnetoresistive (MR) junctions, which have been used very widely [3,4], e.g., a read head in a hard disk drive (HDD) [5] and a cell in a magnetic random access memory (MRAM) [6]. The critical measure of efficient magnetic transport in these devices is an MR ratio, which is defined by
High-sensitive transmission type of gas sensor based on guided-mode resonance in coupled gratings
Published in Journal of Modern Optics, 2018
La Wang, Tian Sang, Junlang Li, Jianyu Zhou, Benxin Wang, Yueke Wang
Optical sensors are powerful tools for many applications such as biomedical research, environmental monitoring and security (1,2). The advantages of optical sensors are high sensitivity, fast response and the ability to be implemented as label-free sensors with no electromagnetic interference. A guided-mode resonance (GMR) optical filter can achieve nearly 100% reflection efficiency as the incident wave is phase-matched to the leaky waveguide modes. The GMR reflective peak is very sensitive to the refractive index (RI) of the film on the structured surface, thus the GMR devices are very suitable for sensing and optical component applications. Recently, the GMR sensors have attracted widespread interests due to their unique advantages, such as good sensitivity, label-free detection, high signal-to-noise ratio, outstanding integrability, and suitable for use in mass-produced portable instruments for practical applications (3–6).