This document discusses ferromagnetic domains and magnetic materials. It explains that ferromagnetism only occurs in certain elements and compounds due to the hypothesis of Weiss involving exchange coupling. Ferromagnetic materials contain small groups of aligned atomic magnets called domains, with the total magnetization of a material being determined by the alignment of its domains. Different domain arrangements occur as the external magnetic field strength increases, resulting in hysteresis loops that vary based on factors like coercive force and the material used, such as in transformer cores.
2. FERROMAGNETIC DOMAINS
ï‚¡ Why only small group of elements and compounds exhibits ferromagnetism
ï‚¡ Hypothesis of Weiss
ï‚¡ Exchange coupling & domains
ï‚¡ Size of domain
ï‚¡ Example of how total magnetization can be zero in single crystals and
polycrystals
ï‚¡ Possible ways by which the material is magnetized to saturation in the
direction of field 2
3. ï‚¡ A typical magnetization curve
ï‚¡ Sequence of domain arrangement with
increasing magnetic field
4. ï‚¡ Different types of hysteresis loops
ï‚¡ Control over the Coercive Force Hc
ï‚¡ Material used for transformer core
ï‚¡ Now, refined techniques are available
