Curie Temperature (Curie Point): Complete Notes, Important Facts, MCQs & Previous Year Questions

 Curie Temperature (Curie Point): Complete Notes, Important Facts, MCQs & Previous Year Questions

What is Curie Temperature?

Curie Temperature (Tc) or Curie Point is the temperature above which a ferromagnetic material loses its permanent magnetism and becomes paramagnetic. It is named after the French physicist Pierre Curie.

At temperatures below the Curie temperature, magnetic domains remain aligned, producing strong magnetism. When the temperature exceeds Tc, thermal agitation disrupts this alignment and the material becomes only weakly magnetic (paramagnetic).

Definition of curie temperature 

Curie Temperature: The critical temperature at which a ferromagnetic material changes into a paramagnetic material.

Let's take look Why Does Ferromagnetism Disappear?

Below Tc:

- Magnetic domains are aligned.

- Strong spontaneous magnetization exists.

Above Tc:

- Thermal energy overcomes magnetic ordering.

- Domains lose alignment.

- Material becomes paramagnetic.

Important Curie Temperatures

Material| Curie Temperature

Iron (Fe)| 770°C (1043 K)

Nickel (Ni)| 358°C (631 K)

Cobalt (Co)| 1121°C (1394 K)

Gadolinium (Gd)| 20°C (293 K)

Exam Trick

Co > Fe > Ni > Gd

(Curie temperature order)

Let's take a look on Curie's Law

For paramagnetic materials:

                               χ = C/T

Where:

- χ = Magnetic susceptibility

- C = Curie constant

- T = Absolute temperature (Kelvin)

Thus, we can say that 

Magnetic susceptibility (χ) is inversely proportional to absolute temperature.

Curie-Weiss Law

For ferromagnetic materials above Curie temperature:

                       χ = C/(T − Tc)

where Tc is the Curie temperature.

Important Competitive Exam Facts of curie temperature

1. Curie Temperature is also called:

- Curie Point

- Critical Temperature for Ferromagnetism

2. At Curie Temperature:

- Ferromagnet → Paramagnet

- Spontaneous magnetization becomes zero

3. Below Tc:

- Ferromagnetic behavior

4. Above Tc:

- Paramagnetic behavior

5. Unit:

- Kelvin (K) or °C

6. Curie Temperature depends on:

- Nature of material

- Internal exchange interaction

7. Magnetic susceptibility:

- Decreases with increase in temperature

8. Diamagnetic substances:

- Do not obey Curie's law.

9. Paramagnetic substances:

- Obey Curie's law.

10. Antiferromagnets:

- Transition temperature is called Néel Temperature, not Curie temperature.

Frequently Asked One-Liners

1. Iron loses ferromagnetism at 770°C.

2. Curie temperature of Nickel = 358°C.

3. Curie temperature of Cobalt = 1121°C.

4. Above Curie temperature, ferromagnets become paramagnetic.

5. Curie's law: χ ∝ 1/T.

6. Curie point is named after Pierre Curie.

7. At Curie point, spontaneous magnetization becomes zero

Previous Year & Exam-Oriented MCQs

Q1. Above Curie temperature, a ferromagnetic substance becomes:

A. Diamagnetic

B. Paramagnetic

C. Antiferromagnetic

D. Superconducting

Answer: B

Q2.The Curie temperature of iron is approximately:

A. 358°C

B. 770°C

C. 1121°C

D. 20°C

Answer: B

Q3. Who discovered the Curie point?

A. Faraday

B. Maxwell

C. Pierre Curie

D. Ampere

Answer: C

Q4.According to Curie's law:

A. χ ∝ T

B. χ ∝ T²

C. χ ∝ 1/T

D. χ ∝ 1/T²

Answer: C

Q5. Which material has the highest Curie temperature?

A. Nickel

B. Iron

C. Cobalt

D. Gadolinium

Answer: C

Q6. The magnetic susceptibility of a paramagnetic material:

A. Increases with temperature

B. Remains constant

C. Decreases with temperature

D. Becomes infinite

Answer: C

Q7. The transition temperature of an antiferromagnetic material is called:

A. Curie Point

B. Boiling Point

C. Néel Temperature

D. Critical Pressure

Answer: C

Q8. Spontaneous magnetization becomes zero at:

A. Melting point

B. Curie temperature

C. Freezing point

D. Boiling point

Answer: B

Last Minute Revision (30 Seconds) of curie temperature  

Curie Temperature = Ferromagnetic → Paramagnetic transition

Iron = 770°C

Nickel = 358°C

Cobalt = 1121°C

χ = C/T (Curie's Law)

 χ = C/(T − Tc) (Curie-Weiss Law)

 Above Tc → Paramagnetic

 Below Tc → Ferromagnetic

 Antiferromagnet → Néel Temperature

Curie Temperatures last minute  revision sheet