Magnetic Interactions: Ferromagnetism & Exchange

This lecture covers the concepts of ferromagnetism, antiferromagnetism, and paramagnetism, explaining the exchange interactions between magnetic moments. It delves into the Curie-Weiss law, band theory of ferromagnetism, and the magnetic anisotropy of materials. The instructor discusses the formation of magnetic domains, domain walls, and the physical mechanism behind giant magnetoresistance. Additionally, the lecture explores the working principles of hard disk drives and the physical mechanisms of magnetic susceptibility. Students will learn about the magnetic Hamiltonian of isolated ions, Hund's rules, and the mean-field approximation for calculating transition temperatures.