Quantum Theory of Spin Waves

Stancil, Daniel D.; Prabhakar, Anil

doi:10.1007/978-0-387-77865-5_2

Cited by 107 publications

(200 citation statements)

References 8 publications

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“…To determine the dependence of M S on the temperature T , the Néel model formalism is used 25 . The saturation magnetization decreases with increasing T and vanishes at the Curie temperature (559 K for YIG).…”

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confidence: 99%

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Optically reconfigurable magnetic materials

et al. 2015

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Structuring of materials is the most general approach for controlling waves in solids. As spin waves-eigen-excitations of the electrons' spin system-are free from Joule heating, they are of interest for a range of applications, such as processing 1-5 , filtering 6-8 and short-time data storage 9 . Whereas all these applications rely on predefined constant structures, a dynamic variation of the structures would provide additional, novel applications. Here, we present an approach for producing fully tunable, two-dimensionally structured magnetic materials. Using a laser, we create thermal landscapes in a magnetic medium that result in modulations of the saturation magnetization and in the control of spin-wave characteristics. This method is demonstrated by the realization of fully reconfigurable oneand two-dimensional magnonic crystals-artificial periodic magnetic lattices.There are two general approaches in designing the properties of a material: changing its chemical composition and structuring. Structuring has been used to control mechanical 10 , optical 11 , and even magnetic properties 12,13 . Periodic variation of the magnetic material's parameters allows the realization of magnonic crystals with novel properties not found in the unstructured material. For example, the dispersion relation of spin waves can be controlled to achieve new schemes for spin-wave-based computing [1][2][3][4][5][14][15][16][17] . The spin-wave dispersion relation depends on many parameters, such as the geometry of the spin-wave waveguide (film thickness and waveguide width), external magnetic field H ext , and saturation magnetization M S . In fact, all of these parameters have already been used to fabricate magnonic crystals [6][7][8]12,13,[18][19][20] : arrays of metallic stripes, etched grooves or antidots, biasing magnetic field or periodic variation of the saturation magnetization using ion implantation.However, all available methods for the fabrication of such spintronic devices result in spatially constant magnetic materials. J. Topp et al. have shown that the parameters of magnetic materials can be changed locally after the rather time-consuming fabrication of the spintronic device 21 -but the functionality of the device stays the same. Here, we present an alternative method for structuring and use it for the manipulation of spin waves-namely fully tunable light patterns (computer-generated holograms), in which optically induced thermal patterns/landscapes modify the spinwave dispersion relation and, hence, the propagation. Thus, the proposed optically reconfigurable magnetic material allows the functionality of a magnetic element to be tuned on demand; the same element can be used as a conduit, a logic gate or a data buffering element.The set-up used for the realization of the light patterns consists of a continuous wave laser as light source, an acousto-optical modulator for temporal intensity control, and a spatial light modulator for spatial intensity control (see Fig. 1a). To study the influence of the thermal gradient ...

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confidence: 99%

“…Indeed, both the experiment and the calculations show vanishing bandgaps due to interference of reflected spin waves for specified lattice shifts. 25) allows the creation of thermal landscapes for the control of spin-wave propagation. In our experiments we used a 5-µm-thick YIG spin-wave waveguide of 1.5 mm width.…”

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confidence: 99%

Optically reconfigurable magnetic materials

et al. 2015

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“…The exchange interactions result in appearing of Ak 2 term in the magnetostatic SW dispersion relation. 43 Thus high exchange constant should lift the frequency up at the fixed k and decrease δ 0 , so the metallization can be visible at larger k values. However, as we have verified numerically, to observe this effect the value of A should be at least two orders of magnitude higher than that of ferromagnetic materials considered in this paper.…”

Section: B Maximizing the Influence Of Metalmentioning

confidence: 98%

Nonreciprocal dispersion of spin waves in ferromagnetic thin films covered with a finite-conductivity metal

Mruczkiewicz

Krawczyk

2014

Journal of Applied Physics

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We study the effect of one-side metallization of a uniform ferromagnetic thin film on its spin-wave dispersion relation in the Damon-Eshbach geometry. Due to the finite conductivity of the metallic cover layer on the ferromagnetic film the spin-wave dispersion relation may be nonreciprocal only in a limited wave-vector range. We provide an approximate analytical solution for the spin-wave frequency, discuss its validity and compare it with numerical results. The dispersion is analyzed systematically by varying the parameters of the ferromagnetic film, the metal cover layer and the value of the external magnetic field. The conclusions drawn from this analysis allow us to define a structure based on a 30 nm thick CoFeB film with an experimentally accessible nonreciprocal dispersion relation in a relatively wide wave-vector range.

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“…As we are neglecting the thermal effects arising from fluctuations of the magnetic moments, we take the low temperature approximation for the Holstein-Primakoff transformations [54]:…”

Section: Appendix: Linear Spin-wave Theory For Disordered Materialsmentioning

confidence: 99%

Competition of lattice and spin excitations in the temperature dependence of spin-wave properties

et al. 2018

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(2018). Competition of lattice and spin excitations in the temperature dependence of spin-wave properties. Physical Review B (PRB), 97 (21). The interplay of magnons and phonons can induce strong temperature variations in the magnetic exchange interactions, leading to changes in the magnetothermal response. This is a central mechanism in many magnetic phenomena, and in the new field of Spin Caloritronics, which focuses on the combination of heat and spin currents. Boson model systems have previously been developed to describe the magnon-phonon coupling but, until recently, studies rely on empirical parameters. In this paper, we propose a first-principles approach to describe the dependence of the magnetic exchange integrals on phonon renormalization, leading to changes in the magnon dispersion as a function of temperature. The temperature enters into the spin dynamics (by introducing fluctuations) as well as in the magnetic exchange itself. Depending on the strength of the coupling, these two temperatures may or may not be equilibrated, yielding different regimes. We test our approach in typical and well-known ferromagnetic materials: Ni, Fe, and Permalloy. We compare our results to recent experiments on the spin-wave stiffness, and discuss departures from Bloch's law and parabolic dispersion. Copyright and re-use policy

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Quantum Theory of Spin Waves

Cited by 107 publications

References 8 publications

Optically reconfigurable magnetic materials

Optically reconfigurable magnetic materials

Nonreciprocal dispersion of spin waves in ferromagnetic thin films covered with a finite-conductivity metal

Competition of lattice and spin excitations in the temperature dependence of spin-wave properties

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