On the Influence of Relativistic Contributions to Spin‐Wave Spectrum on the Thermodynamics of Ferromagnets

Abstract
The influence of magnetostatic contribution and magnetic anisotropy on the thermodynamics of ferromagnets at low T is discussed. Two example are considered: Eu3O4 — a one‐dimensional ferromagnet with large anisotropy constant K1, and EuO with a large spontaneous magnetization. It is shown that these relativistic contributions to spin‐wave spectrum are essential in the range T < TA(TM), where TA(TM) is proportional to K1(2 π M). The question of applicability of restricted statistics to spin waves with an arbitrary k is discussed on the basis of the symmetry of wave functions of the spin‐wave states.