  The effective mass of a magnon in a neodymium magnet is evaluated using Bloch
temperature dependence of spontaneous magnetization. We used the Hall effect
magnetometer and thermo-couple thermometer for measuring of the temperature of
the water in which the encapsulated commercial magnet is immersed. The
experiment can be repeated in every school and methodological remarks for
experimental data processing are given with great detail and attention. The
purpose of the paper is to illustrate the simple relation between the quantum
spectrum of magnons and the easily measured magnetic field of a permanent
magnet.
