magnon - Brief history

In magnetic materials, oscillations in the relative orientations of atomic spins, which correspond to magnetization waves. Magnons are quantum spin waves, appearing as particles capable of scattering with neutrons. Experimentally observable, they are important in understanding the thermodynamic and magnetic properties of magnetic materials.

There is a place named Magnon (pronunciation: ma-nyon) in Gabon, see Magnon, Gabon

A magnon is a collective excitation of the electrons' spin structure in a crystal lattice. In the equivalent wave picture of quantum mechanics, a magnon can be viewed as a quantized spin wave.

Brief history

The concept of a magnon was introduced in 1930 by Felix Bloch in order to explain the reduction of the spontaneous magnetization in a ferromagnet. At absolute zero temperature, a ferromagnet reaches the state of lowest energy, in which all of the atomic spins (and hence magnetic moments) point in the same direction. If one views the perfectly magnetized state at zero temperature as the vacuum state of the ferromagnet, the low-temperature state with a few spins out of alignment can be viewed as a gas of quasiparticles, in this case magnons. Each magnon reduces the total spin along the direction of magnetization by one unit of and the magnetization itself by , where g is the gyromagnetic ratio. The quantitative theory of quantized spin waves, or magnons, was developed further by Ted Holstein and Henry Primakoff (1940) and Freeman Dyson (1956). By using the formalism of second quantization they showed that the magnons behave as weakly interacting quasiparticles obeying the Bose-Einstein statistics (the bosons). The Bose-Einstein statistics of magnons was proven recently (1999) by demonstrating the effect of Bose-Einstein condensation of magnons in an antiferromagnet.