Curie Temperature

Curie temperature is the temperature at which the magnetic substances start losing their permanent magnetic properties and shift to induced magnetism. It is also known as the Curie Point of a substance. When the temperature is low, the dipoles of the magnetic materials become aligned in a specific order.

So, this alignment is the reason which causes magnetism in them. Besides, when the temperature of the material increases to its Curie Point or above, the dipoles of the magnetic material lose their specific order and misalign. Therefore, this misalignment causes the loss of its magnetic properties.

This specific temperature or point got its name after a great French physicist, Pierre Curie. He discovered the relation of magnetic properties to the change in temperature in 1895.

How does Curie’s temperature work?

To understand the actions in a material when heated to or above its Curie temperature, first, let’s briefly understand specific terms. These terms will help you in better understanding the concept.

Ferromagnetic material: 

Ferromagnetism has an association with magnetism in iron-cobalt. It also has an association with nickel and alloys or compounds. Moreover, it can also include one or more than one element listed above. Observations of ferromagnetism are there in gadolinium and some other earth elements.

Besides, these elements are usually scarce. The magnetic atoms get in a sequence in the same direction in ferromagnetic substances. Hence, this orientation reinforces the magnetic field of the substance.

Anti-ferromagnetic material:

In anti-ferromagnetic substances, the magnetic atoms get in an alternative pattern. Here, all the atoms are opposite to each other. The reinforcement of the magnetic field in anti-ferromagnetic substances is lesser than ferromagnetic substances. 

Ferrimagnetic material:

In ferrimagnetic substances, both types of patterns are present spontaneously. Hence, the reinforcement of magnetic fields in ferrimagnetic substances is very weak. Also, the reinforcement of magnetic fields in ferrimagnetic substances is partial.  

Paramagnetic material: 

Paramagnetic materials are those materials in which magnetism is induced through external magnetic fields. Such as inducing magnetic properties in an iron strip. So, the inducing magnetic property in it is through the flowing current. Hence, the iron strip is an example of paramagnetic material.

Working of Curie temperature

When we raise the temperature of these three substances with different magnetic orientations to their Curie temperature, the order of the magnetic atoms disrupts. This disruption causes the loss of the magnetic properties of the material. Therefore, substances are left with a weak magnetic field. This is also known as paramagnetism.

The power of paramagnetism also depends on the type of magnetic material you have heated. The ferromagnetic material gets more paramagnetic power. Next, it is followed by anti-ferromagnetic and then ferrimagnetic substances.

The Curie temperature of the substances can have an arrangement in increasing order. This is according to the type of substance. Moreover, the Curie temperature is always high in the ferromagnetic material. This is followed by the anti and then ferrimagnetic substances. Therefore, cobalt, a ferromagnetic substance, has one of the highest Curie points with 1,121°C or 2,050° F.

To revive the magnetic properties of the ferromagnetic, anti-ferromagnetic and ferrimagnetic substances, cool the substances again to the temperature below their Curie Points.

The Curie temperature of anti-ferromagnetic materials is also known as Néel temperature. It got its name in honour of the French physicist Louis Néel who explained anti-ferromagnetism in 1936.

The increasing order of Curie temperature in ferromagnetic, anti-ferromagnetic and ferrimagnetic substances.

The increasing order of curie temperature is ferromagnetic < antiferromagnetic < ferromagnetic. This is because the atomic magnets in ferrimagnetic have an arrangement in the same direction. Hence, this reinforces the magnetic field. However, the magnetic atoms of anti-ferromagnetic materials have an arrangement in an alternative and opposite order. So, it reinforces the magnetic field less than ferromagnetic substances. At last, the orientation of magnetic atoms in ferrimagnetic substances is a mix of both ferrous and anti-ferrous. So, this is why the reinforcement in them is weak and partial.

Curie – Weiss Law

Curie Law states that the magnetisation in a paramagnet is inversely proportional to the temperature. According to this law, the magnetism of a paramagnet will decrease with the increasing temperature of the paramagnetic material.

M ∝ T

M = C(B/T)

Where,

• M = Magnetism
• C = Curie’s Constant
• T = temperature ( in kelvin)
• B = applied magnetic field

Conclusion 

The Curie temperature is always different in different materials as per their properties. Moreover, they are classified into ferromagnetic materials, anti-ferromagnetic materials and ferrimagnetic materials.