ANTI FERRO AND FERRI MAGNETIC SUBSTANCES

ANTI FERROMAGNETISM

In anti-ferromagnetic substances the spin of dipoles (direction of magnetic moment )of neighborhood domain is equal and opposite in direction.
Examples are Mns, MnO4, FeO, FeCl2 etc.
The susceptibility of anti-ferromagnetism is positive.
These materials exhibit a very low external magnetic field.
The susceptibility decreases with temperature of the material.
They obey Curie’s law. It means if their temperature is increased, they behave as para magnetic substances beyond Curie temperature.

FERRIMAGNETISM (OR FERRITES)

FERRI MAGNETIC MATERIALS ARE ALSO CALLED FERRITES.
These materials produce strong external filed and hence they are used to prepare strong electromagnets.
The direction of magnetic moment of neighborhood domain is not equal but it is in opposite direction.

The examples are MnFe2O4, FeFe2O4 CuFe2O4 etc.

Applications of ferrites:

They are used in the receivers of televisions, and radios .
Used in microwave devices, digital computers, electrical communication devices.

They are used in remote control toys.

Comments

MEISNER EFFECT ON SUPERCONDUCTORS

Meissner effect.

UNIT CELL AND LATTICE PARAMETERS

Unit cell In Crystals the arrangement of particles is described with three dimensional geometrical parallelepiped structure. The unit cell is defined as the smallest size of parallelepiped structure with minimum number of atoms. In a unit cell there are 6 faces and 8 corners. So 8 atoms are required to form a unit cell and all the 8 atoms are located at the 8 corners each. Lattice Lattice is defined as a three dimensional array of atoms. It describes the size and shape of the unit cell. Parameters of a unit cell A unit cell is described by six parameters. These parameters are three dimensions and the angles between them . The Dimensions of unit cell along three axes of a unit cell are represented by (a, b ,c) . The angle between b and c is represented by α, between a and c by β and between a and b by γ. we can identify the structure of crystal by knowing the parameters of unit cell. Properties of unit cell : 1. Unit cell is...

MILLER INDICES - SIGNIFICANCE

Crystal planes : Crystal planes are defined as imaginary planes inside a crystal lattice passing through the atoms along x, y and Z directions. These planes are represented as XY, YZ, ZX and XYZ planes. We cannot find a single plane in a crystal lattice but set of parallel planes are observed. Miller indices: Miller indices are defined as the reciprocals of intercepts of crystal plane. They are used to represent the direction of crystal planes. Miller indices are denoted as the coordinates ( h, k, l ) . h : k : l = 1/p : 1/q : 1/r Miller indices represent the structure of unit cell. Procedure to find Miller indices: 1. Identify the plane intercepts on the x, y and z-axes. 2. Represent intercepts in fractional coordinates as ( p, q, r) 3. Take the reciprocals of the fractional intercepts h : k : l = 1/p : 1/q : 1/r 4. convert the small fractions into integers by multiplying with their least common factor LCM. Significance ...

PHYSICS

Search This Blog