Substance in which the magnetic moment of a single atom is not zero, is know as

Options

A. Diamagnetism
B. Ferromagnetism
C. Paramagnetism
D. Ferrimagnetism

Answer

To solve the question regarding the substance in which the magnetic moment of a single atom is not zero, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Magnetic Moment**:
- The magnetic moment of an atom is a vector quantity that represents the magnetic strength and orientation of a magnet or magnetic material. It arises from the motion of electrons, particularly their spin and orbital movements.

2. **Identify Types of Magnetic Materials**:
- There are several types of magnetic materials, including diamagnetic, paramagnetic, ferromagnetic, and ferrimagnetic materials. Each type has different characteristics regarding their magnetic moments.

3. **Analyze Each Type**:
- **Diamagnetic Materials**: These materials have no unpaired electrons, and their magnetic moments are zero. They are weakly repelled by a magnetic field.
- **Paramagnetic Materials**: These materials have unpaired electrons, leading to a net magnetic moment that is not zero. They are weakly attracted to a magnetic field.
- **Ferromagnetic Materials**: These materials also have unpaired electrons and exhibit a strong magnetic moment. They can retain their magnetization even after the external magnetic field is removed.
- **Ferrimagnetic Materials**: Similar to ferromagnetic materials, but they have unequal opposing magnetic moments, resulting in a net magnetic moment that is not zero.

4. **Conclusion**:
- Among the types of materials discussed, both paramagnetic and ferromagnetic substances have a non-zero magnetic moment due to the presence of unpaired electrons. However, the question specifically asks for a substance where the magnetic moment of a single atom is not zero.
- Therefore, the correct answer is **Paramagnetic** materials, as they have a net intrinsic dipole moment due to unpaired electrons.

### Final Answer:
The substance in which the magnetic moment of a single atom is not zero is known as **Paramagnetic** materials.