Question

in genral explain in clear way what is the diffence between Diamantism , paramgnetism and ferromagnetism? please type your answer

Answer 1

Properties of Diamagnetic Materials

1. There are no atomic dipoles in diamagnetic materials because the resultant magnetic moment of each atom is zero due to paired electrons.

2. Diamagnetic materials are repelled by a magnet.

3. The substances are weakly repelled by the field so in a nonuniform field, these substances have a tendency to move from a strong to a weak part of the external magnetic field.

4. The intensity of magnetization I is very small, negative and proportional to the magnetizing field.

5. Magnetic susceptibility is small and negative.

6. The relative permeability is slightly less than unity.

Diamagnetic Materials Examples and Demonstration

Some of the most common examples of diamagnetic substances are Copper, Zinc, Bismuth, Silver, Gold, Antimony, Marble, Water, Glass, NACL, etc.

Material	χv [× 10−5 (SI units)]
Superconductor	−105
Pyrolytic carbon	−40.9
Bismuth	−16.6
Mercury	−2.9
Silver	−2.6
Carbon (diamond)	−2.1
Lead	−1.8
Carbon (graphite)	−1.6
Copper	−1.0
Water	−0.91

Paramagnetism can further be of two types.

• In the first type, the magnetic moments are found in low concentrations which leads to its separation from one another. Their spins also do not interact.
• In the second type, paramagnetism occurs due to the interactions between the magnetic moment. In this case. the interactions are very weak. Therefore, there is no net magnetization when the applied field is zero.

This type of magnetization is based on Curie’s law. According to the law, paramagnetic materials’ magnetic susceptibility χ is inversely proportional to their temperature. It is represented as;

M = χH = C/T x H

Where,

M = magnetization,
χ = magnetic susceptibility,
C = material-specific Curie constant,
T = absolute (Kelvin) temperature,
H = auxiliary magnetic field.

Properties of Paramagnetic Materials

1. When the net atomic dipole moment of an atom is not zero, the atoms of paramagnetic substances have permanent dipole moment due to unpaired spin.
2. The substances are weakly attracted by the magnetic field.
3. In the non-uniform external magnetic field, paramagnetic substances move from week field region to a strong field region.
4. A paramagnetic rod sets itself parallel to the field because the field is strongest near poles.
5. A paramagnetic liquid in a U-Tube ascends in the limb which is between the poles of the magnet.
6. The intensity of magnetization is very small, positive and directly proportional to the magnetizing field.
7. Magnetic susceptibility is small and positive.
8. The relative permeability is slightly greater than 1. The field inside the material is greater than the magnetizing field.
9. Magnetic field lines become more dense inside paramagnetic substances.
10. Magnetization of paramagnetic substances is inversely proportional to absolute temperature.
11. Paramagnetic substances obey Curie’s law, according to which magnetic susceptibility is inversely proportional to its Absolute Temperature.
12. The magnetic dipole moment of paramagnetic substances is small and parallel to the magnetizing field.

Paramagnetic Materials Examples

At this point, we have learnt that materials that show paramagnetism are paramagnetic. Nonetheless, true paramagnets are those materials that show magnetic susceptibility with respect to the Curie law. They also show paramagnetism regardless of the temperature range. Some of the examples of paramagnetic materials include iron oxide, oxygen, titanium, aluminium, transition metal complexes, etc.

Material	Magnetic susceptibility, [10−5] (SI units)
Tungsten	6.8
Caesium	5.1
Aluminium	2.2
Lithium	1.4
Magnesium	1.2
Sodium	0.72

Superparamagnets

Superparamagnets are the elements that not only show a net paramagnetic response but they also tend to exhibit strong ferromagnetic or ferrimagnetic ordering mostly at a microscopic level. These materials also follow Curie law and have very large Curie constants. Ferrofluids is a superparamagnet.

Ferromagnetism

Ferromagnetism gets its name from the word ‘ferrous’ which means iron which was the first metal known to show attractive properties to magnetic fields. Ferromagnetism is a unique magnetic behaviour that is exhibited by certain materials such as iron, cobalt, alloys, etc. It is a phenomenon where these materials attain permanent magnetism or they acquire attractive powers. It is also described as a process where some of the electrically uncharged materials attract each other strongly. Ferromagnetism is a property that considers not only the chemical make-up of a material but it also takes into account the microstructure and the crystalline structure.

Causes of Ferromagnetism

In a ferromagnetic material in the unmagnetized state, atomic dipoles in small regions called domains are aligned in the same direction. The domains exhibit a net magnetic moment even in the absence of an external magnetizing field.

Examples of Ferromagnetic Materials

Most of the ferromagnetic materials are metals. Common examples of ferromagnetic substances are Iron, Cobalt, Nickel, etc. In addition, metallic alloys and rare earth magnets are also classified as ferromagnetic materials.

Magnetite is a ferromagnetic material which is formed by the oxidation of iron into an oxide. It has a Curie temperature of 580°C. Earlier, it was recognized as a magnetic substance. Magnetite has the greatest magnetism among all the natural minerals on earth.

Properties of Ferromagnetic Materials

1. The atoms of ferromagnetic substances have permanent dipole moment present in domains.
2. Atomic dipoles in ferromagnetic substances are oriented in the same direction as the external magnetic field.
3. The magnetic dipole moment is large and is in the direction of the magnetizing field.
4. The intensity of magnetization (M) is very large and positive and varies linearly with the magnetizing field (H). Hence saturation depends on the nature of the material.
5. The magnetic susceptibility is very large and positive. Magnetic susceptibility Xm = M / H, where M is the intensity of magnetization and H is the strength of the applied magnetic field.
6. The magnetic flux density of the material will be very large and positive. Magnetic field lines become very dense inside ferromagnetic materials. Magnetic flux density B = 0 (H + M), where 0 is the magnetic permittivity of free space, H is the strength of the applied magnetic field and M is the intensity of magnetization.
7. The relative permeability is also very large and varies linearly with the magnetizing field the field inside the material is much stronger than the magnetizing field. They have a tendency of pulling in a large number of lines of force by the material. Relative permeability of material r = 1 + m
8. Ferromagnetic substances are strongly attracted by the field. So in a nonuniform field, they have a tendency to stick at the poles where the field is strongest.
9. If a ferromagnetic powder is placed in a watch glass placed on two poles pieces which are sufficient apart then powder accumulates at sides and shows depression in the middle because the field is strongest at poles.
10. When a ferromagnetic substance is liquefied, it loses ferromagnetic properties due to higher temperature.

Hysteresis

On removing the external magnetic field, a ferromagnetic material doesn’t get demagnetized fully. In order to bring the material back to zero magnetization, a magnetic field in the opposite direction has to be applied. The property of ferromagnetic materials retaining magnetization after the external field is removed is called hysteresis.

The magnetization of the material measured in terms of magnetic flux density (B) when plotted against the external applied magnetic field intensity (H) will trace out a loop. This is called the hysteresis loop.

Retentivity is the magnetic flux density that remains when the magnetizing force is reduced to zero.

Coercivity is the strength reverse magnetizing field that must be applied to completely demagnetize the material.

Curie Temperature

Ferromagnetic property depends on temperature. At a high enough temperature, ferromagnetic substances become paramagnetic. The temperature at which this transition occurs is called Curie’s temperature. It is denoted by TC.

Uses of Ferromagnetic Materials

There are wide applications of ferromagnetic materials in the industry. They are widely used in devices like an electric motor, generators, transformers, telephone, loudspeakers, magnetic stripe at the back of credit cards