DIAMAGNETIC MATERIALS--- When brought into an external field, a weak internal B field is induced inside the material that opposes the external field. |
PARAMAGNETIC MATERIALS--- Brought into an external field, the atoms weakly align with the field. Liquid oxygen provides a classic demonstration, adhering to the pole faces of a large magnet. |
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FERROMAGNETIC MATERIALS--- contain "unpaired" electrons whose magnetic moments align with those of electrons in neighboring atoms. When a ferromagnetic material is brought into an external field, it develops a strong internal field due to electron moments aligning with the field. When the field is removed, most of the alignment still remains, and the material is "permanently" magnetized. |
Magnetic "charges," also called monopoles.? There does not seem to be any physical reason why fundamental particles that are sources of B should not exist, but none have ever been observed despite intensive searches. All known B fields form closed loops. There are no B fields that radiate outward to infinity from a source, or converge from infinity down onto it.