To solve the problem regarding the magnetic dipole moments of different types of materials, we will analyze the magnetic properties of diamagnetic, paramagnetic, and ferromagnetic materials step by step.
### Step-by-Step Solution:
1. **Understanding Diamagnetic Materials:**
- Diamagnetic materials have no unpaired electrons. When placed in a magnetic field, the induced magnetic moment is in the opposite direction to the applied field, resulting in a net magnetic moment of zero.
- Therefore, the magnetic dipole moment for diamagnetic materials is:
\[
\mu_d = 0
\]
2. **Understanding Paramagnetic Materials:**
- Paramagnetic materials have unpaired electrons, which means they possess a net magnetic moment. When placed in a magnetic field, these materials align their magnetic moments with the field, resulting in a non-zero magnetic dipole moment.
- Thus, the magnetic dipole moment for paramagnetic materials is:
\[
\mu_p \neq 0
\]
3. **Understanding Ferromagnetic Materials:**
- Ferromagnetic materials also have unpaired electrons, and they exhibit a strong magnetic moment due to the alignment of magnetic moments of neighboring atoms even in the absence of an external magnetic field. This results in a significant net magnetic dipole moment.
- Therefore, the magnetic dipole moment for ferromagnetic materials is:
\[
\mu_f \neq 0
\]
4. **Comparing the Magnetic Dipole Moments:**
- From the above analysis, we can summarize the relationships:
- \(\mu_d = 0\)
- \(\mu_p \neq 0\)
- \(\mu_f \neq 0\)
5. **Conclusion:**
- The correct relationship among the magnetic dipole moments of diamagnetic, paramagnetic, and ferromagnetic materials is:
\[
\mu_d < \mu_p, \mu_f
\]
- Therefore, the answer to the question is that the magnetic dipole moment of diamagnetic material is zero, while those of paramagnetic and ferromagnetic materials are non-zero.
### Final Answer:
\[
\mu_d = 0, \quad \mu_p \neq 0, \quad \mu_f \neq 0
\]
