The monograph investigates the magnetic properties of rare earth metals, their alloys and compounds, discusses in detail the nature of magnetic phase transitions and magnetostriction, considers magnetoelastic and electrical properties, thermal expansion and magnetocaloric effect. Particular attention is paid to the phenomenon of giant magnetostriction discovered in recent years, the large magnetocaloric effect, invarous properties, and the sharp dependence of magnetization on pressure. The author reveals the physical nature of the processes taking place at the same time. The questions of practical use of the considered phenomena, effects and properties. are presented. For scientists and specialists interested in the physics of magnetic phenomena, the use of new magnetic materials