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Nanomagnets
Published in Ram K. Gupta, Sanjay R. Mishra, Tuan Anh Nguyen, Fundamentals of Low Dimensional Magnets, 2023
Biswanath Bhoi, Mangesh Diware
As discussed in Section 1.2.2, “Magnetization Dynamics”, spin waves are the fundamental quasiparticle excitations of magnetically ordered systems and are also referred to as magnons. Spin waves have been proposed as information carriers for low-power data storage and processing, which has given rise to the field of magnonics [15, 50]. The utilization of magnonic approaches in spintronics gave birth to the field of magnon spintronics. Furthermore, magnonic crystals are critical components for magnon spintronic applications as they enable access to novel multifunctional magnonic devices. These devices can be used as spin-wave conduits and fitters, sensors, delay lines, phase shifters, auto-oscillators’ components, frequency and time inverters, data-buffering elements, power limiters, nonlinear enhancers in a magnon transistor, and components of logic gates [4, 51].
Motivation Behind High Electron Mobility Transistors
Published in D. Nirmal, J. Ajayan, Handbook for III-V High Electron Mobility Transistor Technologies, 2019
The unique property of spintronics is that spins can be transferred without the actual flow of charge. This is called spin current, and it can transfer information without much loss of energy in the form of heat. The only hurdle that remains now is the generation of a large volume of spin current, which could support the electronic devices. In order to create enhanced spin currents, the researchers used the collective motion of spins called spin waves. According to the research one of the spin wave interaction generates spin current ten times more efficiently than using pre-interacting spin waves [83].
Magnon Spintronics
Published in Evgeny Y. Tsymbal, Žutić Igor, Spintronics Handbook: Spin Transport and Magnetism, Second Edition, 2019
A spin wave is a collective excitation of the electron spin system in a magnetic solid [1]. Spin-wave characteristics can be varied by a wide range of parameters including the choice of the magnetic material, the shape of the sample as well as the orientation and size of the applied biasing magnetic field [2, 3]. This, in combination with a rich choice of linear and nonlinear spin-wave properties [4], renders spin waves excellent objects for the studies of general wave physics. One- and two-dimensional soliton formation [5, 6], nondiffractive spin-wave caustic beams [7–10], wave-front reversals [11, 12], and room-temperature Bose–Einstein condensation of magnons [13–16] is just a small selection of examples.
Diamond quantum sensors: from physics to applications on condensed matter research
Published in Functional Diamond, 2022
Kin On Ho, Yang Shen, Yiu Yung Pang, Wai Kuen Leung, Nan Zhao, Sen Yang
Regarding spintronic devices made by YIG thin film, magnons are another exciting playground due to the long coherence length, extended lifetime, and low dissipation. Lee-Wong et al. [56] reported optical detection of magnons, by proximate NV centres, with a broad range of wavevectors in YIG. The magnons were generated by employing the nonlinear parametric excitation. By measuring the PL at different MW frequencies and external magnetic fields, they first demonstrated the intrinsic coupling between exchange spin waves with an NV qubit, as shown in Fig. 6(d). They then modified the magnon band structure by varying the thickness and dimensions of the YIG thin film, showcasing the universality of their technique. The enhanced dipolar interaction changes the magnon dispersion significantly. They further illustrate the discrete values of the magnon wavevectors by patterned the YIG thin film into a microdisk, and several spin-wave modes had been observed. Their experimental findings were supported by theoretical calculations, showing the powerfulness of NV imaging on spin systems.
Understanding and optimization of hard magnetic compounds from first principles
Published in Science and Technology of Advanced Materials, 2021
Takashi Miyake, Yosuke Harashima, Taro Fukazawa, Hisazumi Akai
The electronic density of states, electron and spin densities and magnetic moments are obtained from the eigenvalues and eigenfunctions . Inserting the electron density in eq.(1), the total energy is obtained. The structure is optimized so that the total energy is minimized. To deal with magnetic systems, generalization of DFT for spin-polarized systems was developed [14,15]. The Curie temperature (), crystal-field coefficients, spin-wave dispersion and exchange stiffness are obtained as a post-process calculation using the self-consistent solution [16–20]. A common scheme for evaluating the from first-principles is the following. One computes the intersite exchange couplings by the Liechtenstein method [21], from which a classical Heisenberg model is derived. The Curie temperature is evaluated by solving the model using e.g. mean-field approximation or Monte Carlo simulation. In the mean-field approximation, the is overestimated. Non-stoichiometric systems are hard to treat in a conventional electronic-structure framework, because a large unit cell is required when periodicity is broken. In the Korringa-Kohn-Rostoker (KKR) method in the Green function theory [22,23], however, coherent potential approximation (CPA) [24] is available. In the CPA, a disordered system, e.g. random alloy, is mapped onto a single-impurity problem in an effective medium with an energy-dependent self-energy. The effective medium is determined self-consistently in such a way that the effective-medium Green’s function is equal to the configuration averaged Green’s function of the impurity system (Figure 2).
Exact wave solutions and obliqueness of truncated M-fractional Heisenberg ferromagnetic spin chain model through two analytical techniques
Published in Waves in Random and Complex Media, 2023
M. Raheel, Asim Zafar, Ahmet Bekir, Kalim U. Tariq
Werner Heisenberg first time developed the ferromagnetic spin chains model. This model explains the spin wave of atoms in magnet. This model is used in the statistical physics to explain the ferromagnetism and other phenomena. Consider truncated M-fractional Heisenberg ferromagnetic spin chains model [18] given as follows: where represents the wave function.