The permanent magnetic moment of the atoms of a material is zero. The material

Options

A. must be paramagnetic
B. must be diamagnetic
C. must be ferromagnetic
D. may be paramagnetic

Answer

To solve the question, we need to analyze the properties of different types of magnetic materials based on their permanent magnetic moments.

### Step-by-Step Solution:

1. **Understanding Permanent Magnetic Moment**:
- The permanent magnetic moment of a material is a measure of the material's intrinsic magnetic properties. It indicates how much magnetic moment the atoms of the material possess even in the absence of an external magnetic field.

2. **Types of Magnetic Materials**:
- **Paramagnetic Materials**: These materials have a small, positive permanent magnetic moment. They are attracted to an external magnetic field, but the magnetic moment is not zero.
- **Ferromagnetic Materials**: These materials have a significant permanent magnetic moment. They can retain their magnetization even after the external magnetic field is removed. Thus, their permanent magnetic moment is not zero.
- **Diamagnetic Materials**: These materials have a permanent magnetic moment of zero. They are weakly repelled by an external magnetic field and do not retain any magnetization.

3. **Analyzing the Given Information**:
- The question states that the permanent magnetic moment of the atoms of a material is zero. This directly indicates that the material cannot be paramagnetic or ferromagnetic, as both of these types have a non-zero permanent magnetic moment.

4. **Conclusion**:
- Since the only type of material that has a permanent magnetic moment of zero is diamagnetic, we conclude that the material in question must be diamagnetic.

5. **Final Answer**:
- The material is **Diamagnetic** (Option B).