# Curie's Law

PhysicsMagnetism

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## Introduction

According to Curie’s Law, the magnetization in a paramagnetic material and an applied magnetic field is directly proportional. When the object is heated, the temperature increases, then the magnetization is inversely proportional to be temperature. This law was discovered by the French physicist named Pierre Curie. That is why it is named Curie’s law.

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## Curie’s Law

Most of the elements combined with the compounds possess paramagnetic nature. It is present in compounds that have palladium, iron, platinum, and some rare elements. The atoms which are made up of these elements of compounds have inner shell electrons which are incomplete in nature. This situation causes the unpaired electrons of the elements to spin and top. This will improve the applied magnetic field and make the atoms align.

At the medium strength of the magnetic field, the magnetization M is very linearly proportional to the strength of the applied magnetic field H of a substance.

Magnetization (M) is defined by the formula

$$\mathrm{M = \chi H}$$

where,

$\mathrm{\chi}$ is magnetic susceptibility which is a constant.

When volume V is placed in field H in a particular direction of x, and dH/dx is increasing in the direction rate and you can experience a force of F in the x-direction.

$$\mathrm{F=\chi\mu 0 VH(\frac{dH}{dx})}$$

The magnetic susceptibility of $\mathrm{\chi}$ will be positive; the force is also proportional to the direction of increasing field strength, $\mathrm{\chi}$ will be negative, in the decreasing field strength according to the direction.

In finding $\mathrm{\chi}$ the measurement of force F, in a known field H and known gradient dH/dx is used.

In the type of moments of a free magnetic dipole, these moments are random and these substances have no specific magnetization. With an applied magnetic field, the dipoles are oriented deeply and more dipoles will point against the magnetic field. The substance has a positive susceptibility when it has very net positive magnetization in the direction of the field and is classified as being paramagnetic.

There is another category in which moments are not present normally, but also appear in the external magnetic field. When the susceptibility remains independent of the temperature, due to diamagnetic, the susceptibility of a material can be resolved as positive or negative. The paramagnetic material’s magnetic effect decrease, when temperature increases. This is caused by the increase in the de alignment of atoms.

The magnet which has weak paramagnetic property depends not on the temperature and it is found in many elements which are solid-state metals. Examples of these types of materials are sodium and other alkali metals. This happens when an applied magnetic field affects the electron spins.

## Curie's Law Formula

M = C x (B/T)

where,

M is the Magnetism

B is the Magnetic field in Tesla

T is the absolute temperature in Kelvin and

C is the constant of Curie.

## Curie Temperature

Paramagnetic materials get magnetized when they are placed in a magnetic field, and their magnetization disappears in the absence of magnetic fields. But some materials like iron and nickel have ferromagnetism in the presence of magnetic fields and their properties remain even in the absence of magnetic fields.

The temperature of curie is a point at which the transition from ferromagnetic material turns to paramagnetic on the point of temperature. This type of transition now we seen above are applied in optical storage media for inserting and erasing the data.

In the paramagnetic material, the magnetization is directly proportional to the applied magnetic field of the magnet. And it is inversely proportional to temperature T when the paramagnetic material is heated to a fixed value of the magnetic field.

$$\mathrm{M=\frac{CB}{T}}$$

Magnetic Moment: The magnetic moment induced by the applied field of the magnet is linear to the strength or weakness of the field. The magnetic moment is said to have a sensitive balance to detect the different measurements and effects on the paramagnetic material.

Permeability: Permeability or magnetic constant is the ability of the material to help in the formation of a magnetic field within itself. In other words, the material when exposed to an applied magnetic field gets magnetized.

Curie Point: The material when it loses its magnetic properties at the point of temperature is called Curie point. Certain magnetic materials change their properties at the sharp point at this temperature.

Curie Constant: Curie Constant is a property of the material that is related to its magnetic capability at a certain point of its temperature. The property depending on the material relates to the magnetic susceptibility of the material at its temperature when applied to Curie’s law.

## Conclusion

• Magnetic susceptibility is inversely proportional to the temperature.

• The magnetization is directly proportional to the magnetic field of a paramagnetic material.

## FAQs

Qns 1. Give the Curie's law formula.

Ans. Curie’s law is formulated as M = C x (B/T)

Whereas,

M is the Magnetism

B is the Magnetic field (Unit in Tesla)

T is the absolute temperature in unit Kelvin

C = Curie constant

Curie’s law operates well for high temperatures.

Qns 2. What is the Law of Curie for Para magnetism?

Ans. According to Curie’s Law, a paramagnetic material’s magnetization is inversely proportional to the temperature. This means that the higher the temperature of the material or the increase in paramagnetic property the magnetization of the material decreases.

Qns 3. What is Curie temperature in Paramagnetic Material?

Ans. The temperature at which the transition of paramagnetic materials changes to ferromagnetic material is called Curie temperature. The point of temperature at which the property of material loses its ferromagnetic properties and changes into the paramagnetic property

Qns 4. Mention the Significance of Curie's temperature.

Ans. At the point of Curie temperature, the magnetic property of the ferromagnetic material removes and its paramagnetic material, i.e. the material stays weak magnetism. This happens due to the thermal energy becomes sufficient to overcome the aligning of the material.

Qns 5. Does a Ferromagnetic substance obey Curie's law only above its Curie point?

Ans. The susceptibility decreases with an increase in the temperature of ferromagnetic substances. After Curies point, ferromagnetic substance susceptibility is inversely proportional to its absolute temperature. All ferromagnetic material obeys Curie's law only after it reaches the Curie point.

Updated on 13-Oct-2022 11:19:47