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Paramagnetic solutions get magnetised very faintly in the direction of any externally applied magnetic field. They lose their magnetic properties when the field is removed. They tend to orient themselves where they feel the magnetic field more strongly. Paramagnetic liquids have a permanent magnetic moment or dipole because of the presence of an unpaired electron in their atom. That is why the net dipole moment of these liquids is never actually zero. It can be explained based on the thermal motions that randomise their spin orientation.
Paramagnetic force
Paramagnetic force is exhibited in the phenomenon of paramagnetism where a substance tends to get weakly magnetised upon an external field, unlike ferromagnets that strongly get magnetised in an external magnetic field. The net magnetic moment in them is never zero owing to the presence of unpaired electrons in their atoms. This is why they have a permanent dipole. On applying a magnetic field, this dipole gets oriented in the direction of that field. Because of their weak magnetisation, whenever the magnetic field is removed, the substance loses its magnetisation.
How the paramagnetic solutions get magnetised is entirely based on a law known as Curie’s law. For example, if the temperature increases, the magnetic susceptibility will decrease and the temperature decreases, which leads to an increase in magnetic susceptibility.
Properties
There are certain properties these solutions exhibit. They are –
The atoms of these liquids tend to have a permanent magnetic moment or dipole due to their unpaired electrons present inside them.
They are feebly magnetised in the direction of an externally applied magnetic field.
They tend to move from a weak field magnetic region to a stronger magnetic region in the presence of a non-uniform magnetic field.
These liquids have a small but positive intensity of magnetization which is why they always orient themselves in the magnetic field’s direction.
The magnetic field inside the liquids is higher than the external magnetic field. This is the reason why these liquids have a relative permeability that is a little greater than 1.
The magnetic susceptibility of the paramagnetic liquids is not directly proportional to temperature.
How to prepare a paramagnetic solution?
A paramagnetic solution can be made by using salts of manganese like manganese sulphate or manganese chloride or manganese nitrate are cheaper and easily available on the market. They are weakly magnetised when a magnet is brought close to them, unlike ferromagnets.
To make a proper solution, we need to make a dispersion medium for example dichloromethane.
Dichloromethane is dense; hence we need to saturate it by adding an adequate amount of water. The entire medium is prepared using dichloromethane, water and manganese salt in accurate proportions.
Upon bringing a magnet nearby, the manganese starts to show paramagnetic behaviour and forms a droplet attracting towards the field.
We can impart fluorescence as well by dropping a fluorescent dye in the solution and subjecting it to UV light.
Paramagnetic solution demonstration
Numerous experiments have been conducted worldwide where a paramagnetic solution is placed in a watch glass between two poles of a magnet that are nearby. After some time, there were two observations –
Because of this unique phenomenon, the solution starts to accumulate in the centre because the magnetic field is pretty strong in the middle.
Again when the solution in the watch glass is placed in between two magnets that are wide apart, they start to move towards the two respective poles of the same magnet owing to the strong magnetic field at the poles.
Examples
Paramagnetic substances are those that show magnetic susceptibility which obeys Curie’s law. Sometimes they even show paramagnetism irrespective of any temperature range. They are –
Titanium
Iron oxide
Tungsten
Sodium
Aluminium
Oxygen
Magnesium
Lithium
Manganese
Transition metal complexes
Dysprosium nitrate, manganese salts such as manganese nitrate, manganese chloride or manganese sulphate are paramagnetic salts that are cheap and easily available on the market. They can be used to prepare a paramagnetic solution. Another example can be liquid oxygen which also exhibits paramagnetic behaviour.
Conclusion
Paramagnetic solutions are those that exhibit this phenomenon under the application of a paramagnetic force. They show a feeble magnetisation in the direction of the magnetic field. Their magnetisation also decreases when the magnetic field is removed. They have a permanent dipole or magnetic moment in them because of the presence of unpaired electrons in their atoms. The permanent dipole is because of the thermal motions that cause randomization in their spin orientation. These solutions get accumulated in the middle owing to strong magnetic fields in the centre or move towards poles when they are far away. These liquids get magnetised following Curie’s law. Temperature plays an important role to what extent they will be magnetised. Some of the important paramagnetic solutions include liquid oxygen, and salts of manganese in a denser dispersion medium like dichloromethane, etc.
