Paramagnetic materials

Definition

Paramagnetic materials are substances that have unpaired electrons, allowing them to be attracted to an external magnetic field. This property arises due to the presence of magnetic dipole moments from the unpaired electrons, which align with the applied field, resulting in a net magnetization. Unlike ferromagnetic materials, the magnetization in paramagnetic materials is weak and disappears once the external field is removed.

5 Must Know Facts For Your Next Test

1. Paramagnetic materials are characterized by having one or more unpaired electrons that give rise to magnetic dipole moments.
2. The magnetic susceptibility of paramagnetic materials is typically small and positive, indicating a weak attraction to magnetic fields.
3. Examples of paramagnetic materials include aluminum, platinum, and certain metal ions like iron (in dilute solutions).
4. The alignment of magnetic dipoles in paramagnetic materials occurs only when an external magnetic field is present, and this effect ceases once the field is removed.
5. The strength of the induced magnetization in paramagnetic materials increases with temperature but diminishes as thermal motion disrupts dipole alignment.

Review Questions

• How does the presence of unpaired electrons in paramagnetic materials affect their behavior in a magnetic field?
  • The presence of unpaired electrons in paramagnetic materials leads to the formation of magnetic dipole moments. When these materials are exposed to an external magnetic field, the dipoles tend to align with the field, resulting in a net magnetization. However, this magnetization is relatively weak compared to that seen in ferromagnetic materials and will disappear once the external field is removed.
• Compare the characteristics of paramagnetic and ferromagnetic materials, particularly regarding their response to an external magnetic field.
  • Paramagnetic materials exhibit weak and temporary magnetization when exposed to an external magnetic field due to their unpaired electrons aligning with the field. In contrast, ferromagnetic materials have strong and permanent magnetization, as their magnetic dipoles can align even without an external field. The key difference lies in the strength and permanence of the induced magnetization: paramagnetism is transient while ferromagnetism can persist independently.
• Evaluate how temperature influences the magnetic properties of paramagnetic materials and relate this to their practical applications.
  • Temperature significantly affects the magnetic properties of paramagnetic materials. As temperature increases, thermal agitation disrupts the alignment of unpaired electrons with an external magnetic field, reducing magnetization. However, at lower temperatures, the alignment improves, enhancing their response to magnetic fields. This temperature dependence makes paramagnetic materials useful in applications such as MRI contrast agents, where controlled response to external fields is needed for imaging purposes.

Related terms

Magnetic susceptibility: A measure of how much a material will become magnetized in an applied magnetic field, with paramagnetic materials having positive susceptibility.

Ferromagnetic materials: Materials that have a strong and permanent magnetization due to the alignment of magnetic dipoles even without an external magnetic field.

Curie temperature: The temperature above which ferromagnetic materials lose their permanent magnetism and behave like paramagnetic materials.