Spin Wave

Also found in: Dictionary, Wikipedia.
Related to Spin Wave: Magnon

spin wave

[′spin ‚wāv]
(solid-state physics)
A sinusoidal variation, propagating through a crystal lattice, of that angular momentum which is associated with magnetism (mostly spin angular momentum of the electrons).

Spin Wave


(1) In magnetically ordered media, spin waves are waves of disturbances of the spin ordering. In ferromagnetic materials, antiferromagnetic materials, and ferrites, the spins of atoms and the magnetic moments associated with the spins are strictly ordered in the ground state. Because of the strong exchange interaction between atoms, the departure of the magnetic moment of any atom from its equilibrium position is not localized but propagates through the medium in the form of a wave. Spin waves are an elementary motion of the magnetic moments in magnetic media. The existence of spin waves was predicted by F. Bloch in 1930.

A spin wave, like any wave, is characterized by the dependence of the frequency ѡ on the wave vector k (the dispersion relation). Several types of spin waves can exist in complex magnetic media (crystals with several magnetic sublattices); the dispersion relation of such spin waves depends essentially on the magnetic structure of the substance.

Spin waves can be given a pictorial classical interpretation by considering a chain of N atoms in a magnetic field H where the spacing between adjacent atoms is a (see Figure 1). If the wave vector of the spin wave is k = 0, then all the spins are precessing in phase about the direction of the field H. The frequency of this homogeneous precession equals the Larmor frequency ѡ0. For k ≠ 0, the spins execute inhomogeneous precession: the precessions of the separate spins (1, 2, 3, and so on) are not in phase, and the phase shift between neighboring atoms is equal to ka (see Figure 1). The frequency ω(k) of inhomogeneous precession is greater than the frequency of homogeneous precession ω0. If the forces of interaction between the spins are known, the function ta(k) can be calculated.

Figure 1. Precession of W spin vectors in a linear chain of atoms (instantaneous “picture”)

For long spin waves (ka << 1) in ferromagnetic materials, this function is simple:

ω(k) = ω0 + ωe (ak)2

The quantity ħωe is of the order of magnitude of the exchange integral between neighboring atoms. As a rule, ωe >> ω0. The frequency of homogeneous precession ω0 is determined by the crystal anisotropy and the magnetic field H applied to the crystal: ѡ0= g(βM + H), where g is the gyromagnetic ratio, β is the anisotropy constant, and M is the magnetization at T = 0°K. From a quantum-mechanical consideration of a system of interacting spins it is possible to calculate the dispersion relation of the spin waves for different crystal lattices for an arbitrary ratio of the length of the spin wave and the lattice constant of the crystal.

Spin waves are regarded as corresponding to a quasi-particle called a magnon. At T = 0°K, there are no magnons in magnetic media. At higher temperatures, magnons appear, the number increasing with increasing temperature. The number of magnons in ferromagnetic materials is approximately proportional to T312; in antiferromagnetic materials, the number is approximately proportional to T3. An increase in the number of magnons leads to a decrease in the magnetic ordering. Thus, because of the increase in the number of spin waves with increasing temperature, there is a decrease in the magnetization of a ferromagnetic material; according to Bloch’s law, the change in magnetization is ΔMT) ~ T312.

Spin waves are manifested in the thermal, high-frequency, and other properties of magnetic media. When neutrons are inelasti-cally scattered by magnetic media, spin waves are excited in the media. Scattering of neutrons is one of the most effective methods for experimental determination of the dispersion relations of spin waves (seeNEUTRON DIFFRACTION ANALYSIS).

(2) In nonmagnetic metals, spin waves are oscillations in the spin density of the conduction electrons caused by the exchange interaction of the electrons. The existence of spin waves in nonmagnetic metals is manifested in certain features of electron paramagnetic resonance (EPR), in particular, the ability of metal plates to transmit selectively electromagnetic waves with frequencies close to the EPR frequency.


Akhiezer, A. I., V. G. Bar’iakhtar, and S. V. Peletminskii. Spinovyevolny. Moscow, 1967.


References in periodicals archive ?
The principle of operation is based on the effect of spin wave interference, which is similar to the operation of optical holographic devices.
Different chapters of the book reflect different facets of spin wave confinement, providing a comprehensive description of the effect and its place in modern magnetism.
According to their findings, one of the spin wave interactions (called three-magnon splitting) generates spin current ten times more efficiently than using pre-interacting spin waves.
Recent experiments on quantum gases have utilized this cherished trait of cold atoms for the study of spin waves, a property usually associated with solid-state materials rather than dilute atomic gases.
However, the researchers are still looking at different ways of processing the data carried by the spin waves.
Exploring spin wave dynamics in thin films by coupling to a superconducting qubit complements conventional measurement techniques based on photon, electron or neutron scattering methods, which require highly populated excitations.
InSpin~s final deliverable is to fabricate the first functional spin wave bus with signal input and detection and to use this bus to realize a logic majority gate as the key component for future insulator spintronics.
With traditional Magnonic studies typically geared towards the low GHz range, and nanoplasmonic phenomena primarily focusing on visible light, my proposed platform will also attempt to bridge the so-called THz gap and create ultra-broadband and rapidly tuneable spin wave (SW) based signal generators, manipulators, detectors, and even spectrometers, in the 10200 GHz frequency range.
Alexander Khitun, the lead researcher, who is a research professor at UC Riverside, has been working for more than nine years to develop logic device exploiting spin waves.
Statistical mechanics of magnetic excitations; from spin waves to stripes and checkerboards.
4] we will utilize a procedure based on spin waves what was developed by T.
Magnons are the quanta of spin waves, the dynamic eigen-excitations of a magnetically ordered body.