Lecture 7b Magnetism. Contents 7.5 Magnetic properties of materials 7.6 Soft ferromagnetic materials 7.7 Hard ferromagnetic materials 7.8 Paramagnetism and diamagnetism. 7.5 Magnetic properties of materials.
where χm is the magnetic susceptibility For mu-metal χm is typically 3×104.
where dimensionless μr is called the relative permittivity which in mu-metal may be about 3×104.
(magnetic equivalent of dielectric constant)
Narrow hysteresis loop – less energy dissipation. Good for electromagnets, transformers, motors and generators. ( Eg. soft iron)
Hard ferromagnetic material
Broad hysteresis loop – need large reverse field to demagnetise.
Good for permanent magnets. Eg Steels and alloys (Alnico)7.7 Materials: soft and hard ferromagnetics