Magnetic Materials:

Magnetic materials are those materials which could be either attracted or repelled through a magnet and could be magnetized themselves. The most generally used magnetic materials are steel and iron. The permanent magnet is made of an extremely hard magnetic material, like as cobalt steel that retains its magnetism for long periods of time whenever the magnetizing field is removed.  A temporary magnet is a material which will not retain its magnetism whenever the field is removed.

Permeability (µ) refers to the ability of a material to concentrate magnetic lines of flux.  Those materials which could be simply magnetized are considered to have a high permeability. Associative permeability is the ratio of the permeability of a material to the permeability of a vacuum (µ_o). The symbol for associative permeability is µ_R (mu).

µR =   µ _o/ µ _o where µ_o = 4Φ10^-7 H/m                                          (1-12)

Magnetic materials are characterized as either magnetic or nonmagnetic based on the highly magnetic properties of iron.  Since even weak magnetic materials might serve a useful purpose in a few applications, classification involves the three groups defines below.

Ferromagnetic Materials:   A few of the ferromagnetic materials used are steel, iron, nickel, cobalt, and the commercial alloys, peralloy and alnico. The Ferrites are nonmagnetic but it has the ferromagnetic properties of iron.    Ferrites are created of ceramic material and have associative permeabilities which range from 50 to 200.  They are generally used in the coils for radio frequency (RF) transformers.

Paramagnetic Materials:     These are materials like as aluminum, manganese, platinum, and chromium.  These materials have a associatively permeability of slightly more than one.

Diamagnetic Materials:  These are materials like as antimony, bismuth, zinc, copper, gold, mercury, and silver.  Those materials have an associative permeability of less than one.