Physics of Magnetic Materials
- Department of Solid State Engineering
Origin of magnetic moment. Magnetic susceptibility of materials. Diamagnetism and paramagnetism. Materials with spontaneous magnetization - ferromagnets, antiferromagnets, ferrimagnets. Domain structure and magnetization process. Magnetic relaxation and resonance phenomena.
Elementary solid state physics
- Syllabus of lectures:
1. Diamagnetism and paramagnetism. Orbital and spin magnetic moment of atomic and itinerant electrons in solids. Hund rules and their application for ions of transirtion elements. Larmor precession and diamagnetism of atomic electrons. Diamagnetism of weakly interacting atoms and molecules in non-metallic solids. Landau diamagnetism of itinerant electrons. Diamagnetism of superconductors. Paramagnetism of systems of weakly interacting atoms and ions - Langevin, Brillouin and Van Vleck theory. The influence of crystalline electric field in paramagnetic materials, the quenching of orbital moment. Pauli spin paramagnetism of itinerant electrons. Methods of measurement of magnetic susceptibility. 2. Ferromagnetism. Experimental determination of participation of orbital and spin motion of electrons to the formation of magnetic moment of materials. Weiss phenomenological theory of ferromagnetism. Heisenberg quantum theory. Direct exchange interaction of electrons. Bethe - Slater criteria of ferromagnetism. Holstein - Primakoff theory of spin waves. Temperature dependence of spontaneous magnetization of ferromagnets - Bloch law. Band theory of metallic ferromagnets. Occurrence of ferromagnetism in metals, compounds and alloys. Thermal, mechanical and electrical phenomena associated with ferromagnetic state. Phase transitions in ferromagnets. 3. Antiferromagnetism and ferrimagnetsm. Typical crystal structures of antiferromagnets and ferrimagnets. Normal, inverse and mixed spinels, perovskites and garnets. Neel theory of molecular field, superexchange. Spin wave theory of antiferromagnets and ferrimagnets. More general types of exchange effects and magnetic order. Use of elastic and inelastic neutron scattering for the study of magnetic order and elementary magnetic excitations. 4. Domain structure and magnetization process. Origin of domain structure in magnetically ordered materials and methods of its observation. Exchange, magnetocrystalline, magnetoelastic and demagnetisation energy in magnetic materials. Bloch and Neel transition walls between domains, various types of domains. Magnetization curve, contribution of individual mechanisms in the magnetization process. Initial permeability, coercive force, remanent magnetization. Soft and hard magnetic materials. Magnetic thin films. Practical applications of magnetic materials. 5. Magnetic relaxation and resonance processes.
- Syllabus of tutorials:
- Study Objective:
Knowledge: ^^Magnetism of solids. ^^Skills: ^^Explanation of diamagnetism, paramagnetism and spontaneous magnetic ordering in solids, description of magnetization and relaxation processes, application of magnetic materials in praxis.
- Study materials:
Key references: ^^. Morrish A.H. : The Physical Principles of Magnetism, John Wiley and Sons, New York 1965, ^^Recommended references: ^^. Chikazumi S.: Physics of Magnetism, John Willey and Sons, New York 1964.
- Further information:
- No time-table has been prepared for this course
- The course is a part of the following study plans:
- Inženýrství pevných látek (compulsory course of the specialization)