THE INTRODUCTION OF MAGNONS

BLOCH, FELIX.

Zur Theorie des Ferromagnetismus.

Berlin, Springer, 1930. 8vo. In contemporary half cloth with gilt lettering to spine. In "Zeitschrift für Physik", Bd. 61, 1930. Entire volume offered. Stamp to title page and light wear to extremities, otherwise fine and clean. VIII, 878 pp.

First appearance of Bloch's seminal paper in which he introduced the concept of magnons as the elementary excitations in ferromagnetic crystals.

The concept of Magnon was introduced 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. As the temperature increases, more and more spins deviate randomly from the common direction, thus increasing the internal energy and reducing the net magnetization. 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.

Order-nr.: 49119