Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
We know when the ferromagnetic material is subjected to external field, there is an increase in the value of the resultant magnetic moment due to two process, viz.,
Magnetic Properties of Materials
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
When a ferromagnetic material is made to undergo through a cycle of magnetisation, the variation of M (Magnetisation) with respect to H (Applied field) can be represented by a closed hysteresis loop (or) curve.
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
The domain in ferromagnetic solid is understandable from the thermodynamical principle, (i.e.,) in equilibrium the total energy of the system is minimum.
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
We can observe that ferromagnetic materials such as iron does not have magnetisation unless they have been previously placed in an external magnetic field.
Magnetic Properties of Materials
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
The Weiss theory of ferromagnetism explains about the molecular field but it is not possible to explain large value of internal field.
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
The molecular magnets in the ferromagnetic material is aligned in such a way that, they exhibit a magnetisation even in the absence of an external magnetic field.
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
The metals like Fe, Co, Ni etc exhibit magnetisation even in the absence of external field. Therefore Weiss gave a molecular field theory.
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
In diamagnetic material there are equal number of electron spins which are randomly oriented and hence the net magnetic moment is zero.
Properties, Effect of external field, Examples
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
In a ferromagnetic material the number of unpaired electrons are more. Most of these spin magnetic moments point in one direction.
Properties, Effect of external field, Examples
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
In the case of paramagnetic materials, the spins in two opposite directions will not be equal.
Properties, Effect of external field, Examples
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
In a diamagnetic material, the electron orbits are more or less random, and mostly all the magnetic moments are cancelled.
Subject and UNIT: Physics for Information Science: Unit III: Magnetic Properties of Materials
Magnetic materials are classified according to the presence or absence of the permanent magnetic dipoles.