  An experimental method is suggested for the determination of the rate of
magnetic phase transitions. The method is based on the measurement of the
change of magnetic susceptibility of a ferromagnetic sample in the vicinity of
the phase transition in response to an abrupt change of the sample temperature.
This paper describes the measurement of the change of the magnetic
susceptibility of a thin gadolinium plates, cooled by water-flow at a
temperature below the Curie point (Tc = 292 K). It was found that the
relaxation time of the magnetic susceptibility of gadolinium in the temperature
range from 289.9 to 291.3 K can be approximated using the Landau-Khalatnikov
equation with a kinetic coefficient value gamma = 3.9x10-8 cm3/(ergxs). The
linear approximation does not fit well in the range from 291.3 to 293.2 K. The
fundamental restriction of specific power of the magnetocaloric refrigerator
(made by gadolinium plates) was estimated.
