(Last Updated on : 12/12/2012)
The permanent magnets are made from a very wide range of magnetic materials. These materials vary in the nature of their elements and their composition. Each of these magnetic materials has its own values, characteristics and consequently its own uses.
Alnico is the most commonly used alloy in the manufacture of permanent magnets. It consists of Aluminium, Nickel, Iron and Cobalt. The cobalt is costlier than the others and Iron is the cheapest of all.
The magnetic materials or magnetic substances are the different metallic alloys from which magnets are made. Depending on their nature and content, the magnetic materials are broadly classified in three main categories:
* Ferromagnetic material
* Paramagnetic material and
* Diamagnetic material
The ferromagnetic materials have very large values of magnetic permeability. They have the highest degree of magnetisation. These are the magnetic materials, which are found to be attracted by magnets or magnetic fields. Iron, Steel, Nickel and Cobalt are ferromagnetic materials.
Again these ferromagnetic materials have their own different properties. For example, the properties of Iron and Steel are different. Soft iron has far greater retentive than steel, but has far less coercive. Steel can retain magnetism for a long time, whereas soft iron loses it earlier. Therefore, soft iron is used in electromagnets and steel is used for permanent magnets.
The paramagnetic materials are weakly attracted by the magnets when placed in a magnetic field. The paramagnetic materials feel an attractive force towards the strongest part of the field when they are placed in a non-uniform field. Aluminium
, Chromium, Copper sulphate, Manganese, Palladium, Platinum, Potassium and Tungsten, etc are examples of paramagnetic materials.
The diamagnetic materials are not attracted by magnets. They move from stronger to weaker parts of magnetic field and are characterised by negative susceptibility. The examples of diamagnetic materials are Antimony, Bismuth, Copper, Diamond, Gold, Mercury, Silver, Sulphur, Tin and Zinc.
Gases and liquids are also included to the classes of paramagnetic or diamagnetic materials. Air and oxygen are paramagnetic while Alcohol, Hydrogen, Nitrogen and water are diamagnetic in their nature.
Permanent alloy magnets are generally used for door latches, fans, filter coils, gramophones, loud speakers, magnetos, magnetic generators, magnetic separators, meters, radios, scooters, sugar mills, telephones, television receivers, toy-motors, and other novelties.