Diamagnetism

Definition

Diamagnetism is a fundamental property of all materials, where an applied magnetic field induces a magnetic moment in the opposite direction to the applied field. This phenomenon arises from the orbital motion of electrons within atoms and molecules, which creates a small magnetic field that opposes the external magnetic field.

5 Must Know Facts For Your Next Test

1. Diamagnetism is a universal property of all materials, but it is typically very weak and can be overshadowed by other forms of magnetism, such as paramagnetism and ferromagnetism.
2. Diamagnetic materials, such as copper, gold, and water, are slightly repelled by magnetic fields and have a negative magnetic susceptibility.
3. The diamagnetic response is caused by the induced currents within the material, which generate a magnetic field that opposes the applied magnetic field, in accordance with Lenz's law.
4. Superconductors are perfect diamagnets, as they completely expel magnetic fields from their interior, a phenomenon known as the Meissner effect.
5. Diamagnetism plays an important role in the field of magnetic resonance imaging (MRI), where it is used to create contrast between different tissues in the body.

Review Questions

• Explain the origin of diamagnetism and how it differs from other forms of magnetism.
  • Diamagnetism arises from the orbital motion of electrons within atoms and molecules, which creates a small magnetic field that opposes an applied external magnetic field. This is in contrast to paramagnetism, where the magnetic moments of individual atoms or molecules align with the external field, and ferromagnetism, where materials exhibit a strong magnetic moment even in the absence of an external field due to the alignment of electron spins. Diamagnetism is a universal property of all materials, but it is typically very weak compared to these other forms of magnetism.
• Describe the role of diamagnetism in the Meissner effect and its importance in magnetic resonance imaging (MRI).
  • Superconductors are perfect diamagnets, meaning they completely expel magnetic fields from their interior. This phenomenon is known as the Meissner effect and is a direct consequence of the diamagnetic properties of the material. In the context of MRI, diamagnetism plays a crucial role in creating contrast between different tissues in the body. The slight diamagnetic differences between various tissues, such as fat and water, can be detected by the MRI scanner and used to generate high-resolution images of the internal structures of the body.
• Analyze the relationship between diamagnetism, Lenz's law, and the induced currents within a material.
  • The diamagnetic response of a material is directly related to Lenz's law, which states that the direction of the induced current in a material is such that it opposes the change in the magnetic field. When a material is placed in an external magnetic field, the induced currents within the material generate a magnetic field that opposes the applied field, resulting in the diamagnetic effect. This is a fundamental property of all materials and is a consequence of the orbital motion of electrons, which creates a small magnetic moment that acts to shield the material from the external magnetic field. Understanding this relationship between diamagnetism, Lenz's law, and induced currents is crucial for explaining the behavior of materials in magnetic fields and their applications in various fields, such as MRI and superconductivity.

Related terms

Paramagnetism: Paramagnetism is a form of magnetism that occurs when an applied magnetic field causes the magnetic moments of atoms or molecules to align, resulting in a net positive magnetic susceptibility.

Ferromagnetism: Ferromagnetism is a type of magnetism where materials exhibit a strong magnetic moment even in the absence of an external magnetic field, due to the alignment of the magnetic moments of electrons within the material.

Magnetic Susceptibility:

Magnetic susceptibility is a measure of how easily a material can be magnetized in response to an applied magnetic field, and it is a fundamental property that distinguishes different types of magnetic materials.