Subject: Physics
There are three types of magnetic materials. They are:
Those substances which are feebly magnetized in the direction opposite to the applied field are called diamagnetic material. Examples of diamagnetic materials are bismuth, copper, water, mercury, alcohol, argon, gold,tin, mercury, antimony etc. The magnetic moment of atoms of a diamagnetic material is zero. They acquire induced dipole moments when the material placed in an external magnetic field. These moments are in opposite in the direction to the applied field.
Those materials which are weekly magnetized in the same direction of the applied magnetic field are called paramagnetic material. The examples of paramagnetic materials are aluminum, chromium, oxygen, manganese, alkali, alkaline earth metal etc.
The paramagnetic materials have permanent magnetic moments. These moments interacts weekly with each other and randomly orient in the different direction.
Some Properties
The ferromagnetic materials are highly magnetized in a magnetic field. The examples of ferromagnetic materials are iron, nickel and cobalt, and their alloys such as alnico. Gadolinium and dysprosium are ferromagnetic at low temperature.
Each atom of ferromagnetic substance has a permanent magnetic substance; in the unmagnetised state, the atomic and molecular dipoles are arranged in random so the net magnetic moment is zero. There is a strong interaction with neighboring atoms which keeps their magnetic moment aligned parallel in small regions even in the absence of an external field. These small regions with the volume ranging between 10-12 to 10-8 m3 are called domains. When the material is placed in an external field Be, the domains tend to orient themselves parallel to field B0. As the applied field becomes stronger, the domains, having magnetic moments not aligned with the field, become very small and when the domains fully align to the applied field, the material attains magnetic saturation. On removing the field, the domain walls do not move completely into previous positions. This means material retains a magnetization in the direction of the applied field.
References
Manu Kumar Khatry, Manoj Kumar Thapa,et.al Principle of Physics. Kathmandu: Ayam publication PVT LTD, 2010.
S.K. Gautam, J.M. Pradhan. A text Book of Physics. Kathmandu: Surya Publication, 2003.
Those substances which are feebly magnetized in the direction opposite to the applied field are called diamagnetic material.
Those materials which are weekly magnetized in the same direction of the applied magnetic field are called paramagnetic material.
The ferromagnetic materials are highly magnetized in magnetic field. The examples of ferromagnetic materials are iron, nickel and cobalt, and their alloys such as alnico.
These small regions with the volume ranging between 10-12 to 10-8 m3 are called domains.
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