Diamagnetism and Paramagnetism |Ferromagnetism and Antiferromagnetism | Magnons

Magnetism is the topic which can't be separated from Quantum Mechanics.

Three principal of magnetic moment-

•  The spin with which electrons are endowed

• Orbital angular momentum about the nucleus

• The change in the orbital momentum induced by an applied magnetic field.

First two effects give paramagnetic contributions 

And the third gives dimagnetic contribution.

Magnetic Susceptibility

Magnetization M is defined as the magnetic moment per unit volume.

Magnetic susceptibility is the measurment of the magnitization which substance get after entering into magenetic field.

 χm = M/H

When  χm >0, means Paramagnetism.

And  χm <0, means diamegnetism.

Also, substance with nagetive magenetic susceptibility is caled diamegnetic.

Paramagnetism

Paramagnetism is the type of magnetism where materials are weekly attracted.

Induced magnetic field is in the direction of applied magnetic field.

Paramagnetic and ferromaganetic substance attract each other.

In ferromagnetic and paramagnetic materials, force of magnetic dipoles dominats the weak diamagnetic force.

Diamagnetism

When magnetic field is applied to an atom, it leads to change in thr orbital velocity of its electron which leads to dimagnetism.

 

MAterials having diamagnetic property repell eachother.

Usually diamegnetic materials has weak diamagnetism but superconductors are the example of substance with high diamagnetism.

Ferromagnetism and Antiferromagnetism

Ferromagnetism

A ferromagnet has a spontaneous magnetic moment. The existence of a spontaneous moment suggests that electron spins and magnetic moments are arranged in a regular

manner. 

    

Permanent magnetic are made from ferromagnetic metrials only.

there are two types of ferromegnetic substance.

First with which is soft in nature and the second one which s hard in nature.

permanenty magnets are made up of hard feromamnetic material.

Antiferromagnetism

In an antiferromagnet two spin lattices are equal, but antiparallel. In a ferri-

magnet two lattices are antiparallel, but the magnetic moment of one is

larger than the magnetic moment of the other.

In an antiferromagnet the susceptibility above the Neel temperature has the

form x = 2C/(T + θ).

Magnons

Quantized spin waves are called Maganons.

To find the relation between ω and k,

scientists need to quantize magnon energy and interoret the quantization in terms of spin reversal.

Single-domain Particles

The dominant industrial and industrial applications of ferromagnetism are in magnetic recording devices, wherever the magnetic material is within the of single-domain particles or regions. the whole worth of the productic magnetic devices for recording could also be comparable the whole worth semiconductor device production and greatly exceeds the worth of superconducting device production, the latter being control back by low important temperatures, as compared with magnetic Curie temperatures. The magnetic recording devices or recollections usually square measure within the style of exhausting disks in computers and tape in video and audio recorders.