Types of Para Magnetic Materials

This article discusses types of paramagnetic materials. Materials that get faintly magnetised in the direction of a magnetic field are paramagnetic.

Magnetic properties of materials

Before going into the types of paramagnetic materials, we first need to understand some of the magnetic properties these materials exhibit.

Magnetisation intensity – is when there is no magnet; the magnetic dipole equals zero. However, in the presence of an external magnetic field, a magnetic moment or dipole gets created. The net magnetic moment or dipole per unit volume is called magnetic intensity.

Magnetic intensity – is the externally applied magnetic field that induces magnetic properties in a material.

Magnetic susceptibility – is when a magnetic field is present, the magnetic intensity is directional to the applied magnetic field.

Retentivity – is the capacity to retain magnetisation.

Coercivity – is the capacity to remain magnetised in an external magnetic field and withstand without being demagnetised.

Owing to these properties, three broad phenomena occur in materials – ferromagnetism, paramagnetism and diamagnetism.

Ferromagnetism – they show the properties of a magnet and are strongly magnetised. They orient themselves in the direction of an external magnetic field. They act more like permanent magnets.

Paramagnetism – in the direction of a magnetic field, they get faintly magnetised. The net dipole in them is never zero because of unpaired electrons in them. They get demagnetised upon removal of the field.

Diamagnetism – they are very weakly repelled in a magnetic field. They align themselves in the opposite direction, unlike Ferro or paramagnetic substances.

Paramagnetic force

Paramagnetic substances exhibit this kind of phenomenon. Paramagnetism is the phenomenon where a substance gets weakly magnetised in the presence of an externally applied magnetic field, unlike ferromagnets. They always have a permanent dipole. Whenever a field is present, the dipole orients itself in the direction of the field accordingly. The net magnetic dipole in them is not zero because of the presence of electrons, which are unpaired in their atoms.

Although the magnetic susceptibility of a material is based on Curie’s law, it says that the magnetic susceptibility of the paramagnetic materials is never directly proportional to temperature. As temperature decreases, the magnetic susceptibility will increase and the other way round.

How many types of paramagnetic materials are there?

There are further two types by which these materials can be defined –

In the first type, the spins do not interact with each other. The magnetic moments in them are found in too low concentrations, which leads to their separation from one another.

In the second type, the spins start to interact with each other. Although the interactions are weak, still, paramagnetism occurs due to this. Hence, there is no net magnetisation when the applied external field is removed.

Properties

There are certain properties of these kinds of liquids. They are –

Due to the presence of electrons in their unpaired state, the atoms of these liquids tend to have a permanent magnetic moment or dipole.

Along the direction of an externally applied magnetic field, they are feebly magnetised.

When a non-uniform magnetic field is present, they tend to move from a weak magnetic field region to a stronger magnetic region.

The magnetic field inside the liquids is higher than the external magnetic field. This is why these liquids have a relative permeability that is a little greater than 1.

The magnetic susceptibility of those liquids is never directly proportional to temperature.

These liquids have a low but positive magnetisation intensity, which is why they always align themselves in the direction of magnetic fields.

Examples

Paramagnetic substances show magnetic susceptibility, obeying Curie’s law. Irrespective of any temperature ranges even, sometimes they show paramagnetism. Some paramagnetic materials include iron oxide, dysprosium nitrate, oxygen, magnesium, tungsten, sodium, titanium, aluminium, and manganese salts such as manganese nitrate, manganese chloride or manganese sulphate, lithium, and transition metal complexes, to name a few.

Conclusion

In the direction of the magnetic field, paramagnetic substances show a faint magnetisation. When the magnetic field is removed, their magnetisation also decreases. They have a permanent dipole or magnetic moment in them. This is because of the presence of electrons in their unpaired states inside the atoms. They get magnetised following Curie’s law. Temperature plays an essential role to what extent they will be magnetised. The prime question becomes how many types of paramagnetic materials are there. It is classified further whether the spins interact with each other. Some of the most common paramagnetic materials are tungsten, oxygen, sodium, magnesium, iron oxide, etc. Numerous experiments have been conducted on these substances to demonstrate this phenomenon.