Magnetic Properties

Magnetism is a natural force that is produced by the movement of electric charges. Some of these motions are microscopic and occur within magnets, which are a type of magnetic material. The magnetic fields created by moving electric charges, or magnets themselves, have the ability to attract or repel other magnets, as well as alter the motion of other charged particles.

Magnetic Field: 

A magnetic field is an imaginary line of force that surrounds a magnet and which allows other ferromagnetic materials to be repelled or attracted to it depending on their magnetic properties.

The magnetic field lines are formed for a variety of reasons, including the orbital movement of electrons and the flow of current through a conductor.

Magnetic field lines have certain characteristics.

According to convention, magnetic field lines enter the earth through the south pole and exit through the north pole.

Close to the magnet’s poles, the magnetic field lines are particularly strong.

There is no possibility of magnetic field lines intersecting with one another in this environment.

The strength of a magnet is proportional to the closeness of the magnetic field lines between them.

Magnitude of the magnetic field

Consider the case where a current-carrying coil has generated a magnetic field, denoted by the letter H.

H = nI/L(A/m) nI/L(A/m)

With respect to the solenoid, n denotes the number of turns and l denotes the length of the cylinder.

Magnetic Flux Density is a measure of how much magnetic flux is present in a magnetic field (B). It is known as Magnetic Flux Density when a substance is exposed to a magnetic field H. The density of magnetic field lines passing through the substance per square metre is measured when a substance is exposed to a magnetic field H. It is provided by

B = X H (Tesla or weber /m2) is the unit of force.

Where is referred to as the Permeability and is defined as the extent to which a substance can be magnetised.

The value of permeability in vacuum can be calculated using the formula

m = 4px 10-7(H/m) m = 4px 10-7(H/m)

Magnetic Dipole

Magnetic dipole movement is present in a current loop. As a result of the orbital motion of each electron in an atom, each electron has a magnetic moment. Apart from that, each electron at rest has an unchanging angular momentum, which is referred to as spin angular momentum, that can be measured. This magnetic moment has a fixed magnitude of s = 9.285*10-24 J/T and a fixed direction of rotation.

Consequently, the magnetic moment produced by an atom is a vector sum of magnetic moments generated by orbital movement and spin angular momentum.

The magnetic moments of electrons in an atom have a tendency to cancel out in pairs, which is known as pair cancellation. Taking helium as an example, the magnetic moments of the atom cancel each other out.

When this cancellation does not occur, the magnetic moment of an atom does not become zero in some instances. A magnetic dipole can be used to represent these types of atoms.

As a rule, magnetic moments of atoms are distributed randomly, and there is no net magnetic moment in any volume of material containing hundreds of thousands of atoms. When the material is kept in an external magnetic field, however, torques act on the atomic dipoles, and these torques cause them to align themselves parallel to the field. It is possible to increase the degree of alignment by increasing the strength of the applied field and also by decreasing the temperature of the applied field. When a sufficiently strong field is applied, the alignment is nearly perfect, and we refer to this as the material being magnetically saturated.

When the atomic dipoles are aligned, either partially or completely, in any small volume of the material, there is a net magnetic moment in the direction of the field.

The magnetization vector I is defined as the magnetic moment per unit volume of the magnetization vector. It is referred to as the intensity of magnetization or simply magnetization in some circles.

As a result, I = M/V.

Where M is the magnetic moment measured in ampere-metres.

2 V is the volume of a container.

The ampere/metre unit of I is used.

Magnets are classified according to their magnetic properties.

Magnets can be classified into the following categories based on the characteristics described above:

• Diamagnetic

• Para-magnetic

• Ferro-magnetic

• Ferri-magnetic

• Anti-ferromagnetic materials

Diamagnetic substance

Substance With Diamagnetic Properties

Diamagnetic substances are repelled by magnets due to the fact that they produce negative magnetization when exposed to a magnetic field. A diamagnetic substance has no net magnetic moment because when an external field is applied to it, the magnetic moment of electrons is aligned in the opposite direction of the applied field. This results in the net magnetic moment being zero. Every element in the periodic table possesses the property of diamagnetism, but only a few elements, such as Cu, Al2O3, Si, and Zn, have a stronger diamagnetic property than the rest.

Paramagnetic Substance

Substance with Paramagnetic Properties

Because the net magnetic moment is not completely cancelled out in paramagnetic material, there is a small magnetic moment present in the material. In paramagnetic material, the magnetic moments are randomly aligned, and when subjected to an external magnetic field, these magnetic moments align themselves in the direction of the applied magnetic field H. This is known as the polarisation effect. Aluminum, Cr, Mo, Ti, and Zr are examples of paramagnetic materials.

Ferromagnetic Substance

Substance with Ferromagnetic Properties

Ferromagnetism is a property of materials that, in contrast to diamagnets and paramagnets, has the tendency to retain their magnetism even when the magnetic field is removed. This phenomenon is also referred to as Hysteresis, and the graph depicting the relationship between variations in magnetism and magnetic field is referred to as the Hysteresis Loop. However, ferromagnetic materials have a tendency to lose their magnetic properties at a certain point or temperature. Curie point or Curie Temperature is the temperature or point at which Curie’s experiments were completed.

Ferri magnetic substance

Substance with Ferri-Magnetic Properties

When comparing a ferromagnetic material and ferri-magnetic material, the most significant difference is that some magnetic domains in a ferri-magnetic material point in the same direction as other magnetic domains, whereas other magnetic domains point in the opposite direction. In contrast, all of the magnetic domains in a ferromagnetic material point in the same direction as one another.

Anti ferromagnetic substance

Substance that is anti-ferromagnetic

Magnetic moments of atoms or molecules in Anti-Ferromagnetic materials, which are usually related to the spin of electrons, align in a regular pattern with neighbouring spins in opposite directions, resulting in a regular pattern of alignment.

MnO exhibits anti-ferromagnetism, which is a rare phenomenon.

Curie Law

It is known as the Curie Law that the magnetic susceptibility of paramagnetic materials is inversely proportional to their absolute temperature.

The magnetic susceptibility of paramagnetic materials decreases as the temperature of the material rises, and the converse is true. The magnetic susceptibility of ferromagnetic substances does not change with temperature.

χ = C/T

where C denotes the Curie constant,

in accordance with Curie’s law

Defining Curie temperature (T) or Curie temperature (T) is the temperature above which the behaviour of a ferromagnetic material resembles that of a paramagnetic material is observed. Known as the Curie temperature, it is the absolute minimum temperature at which a ferromagnetic substance can be converted into a paramagnetic substance. Its values vary depending on the ferromagnetic material, for example, for Ni, Fe, and Co.

In the case of Fe, the temperature is 358° C, in the case of CO, the temperature is 770° C, and the temperature is 1120° C. Suddenly, the ferromagnetism of the substances disappears when the temperature is reached. 

Conclusion –

The magnetic field lines are formed for a variety of reasons, including the orbital movement of electrons and the flow of current through a conductor. The strength of a magnet is proportional to the closeness of the magnetic field lines between them. As a result of the orbital motion of each electron in an atom, each electron has a magnetic moment. The magnetic moments of electrons in an atom have a tendency to cancel out in pairs, which is known as pair cancellation. A diamagnetic substance has no net magnetic moment because when an external field is applied to it, the magnetic moment of electrons is aligned in the opposite direction of the applied field.