Paramagnetism

Definition

Paramagnetism is a form of magnetism where certain materials exhibit a weak positive magnetic susceptibility, meaning they are slightly attracted to an external magnetic field. This occurs due to the presence of unpaired electrons within the atoms or molecules of the material, which create small magnetic dipoles that can align with an applied magnetic field.

5 Must Know Facts For Your Next Test

1. Paramagnetic materials, such as oxygen, aluminum, and platinum, exhibit a positive magnetic susceptibility and are attracted to magnetic fields.
2. The strength of a paramagnetic material's response to a magnetic field is directly proportional to the strength of the applied field and the number of unpaired electrons present.
3. Paramagnetic materials do not retain their magnetism when the external magnetic field is removed, unlike ferromagnetic materials.
4. Paramagnetism is a temperature-dependent phenomenon, with the magnetic susceptibility decreasing as temperature increases, as described by the Curie law.
5. Paramagnetic materials are often used in magnetic resonance imaging (MRI) devices, where they are used to enhance the contrast of images by aligning with the strong magnetic fields.

Review Questions

• Explain how the presence of unpaired electrons in a material leads to paramagnetism.
  • The presence of unpaired electrons in a material creates small magnetic dipoles within the atoms or molecules. These magnetic dipoles can align with an external magnetic field, causing the material to exhibit a weak positive magnetic susceptibility, or paramagnetism. The strength of the paramagnetic response is directly proportional to the number of unpaired electrons present in the material.
• Describe the relationship between temperature and the magnetic susceptibility of a paramagnetic material.
  • The magnetic susceptibility of a paramagnetic material is inversely proportional to its temperature, as described by the Curie law. As the temperature of a paramagnetic material increases, the thermal energy of the system increases, causing the magnetic dipoles to become more disordered and less aligned with the external magnetic field. This results in a decrease in the material's magnetic susceptibility, making it less responsive to the applied magnetic field.
• Analyze the role of paramagnetism in the application of magnetic resonance imaging (MRI) technology.
  • Paramagnetic materials, such as gadolinium-based contrast agents, are often used in MRI devices to enhance the contrast of images. These paramagnetic materials are introduced into the body and align with the strong magnetic fields generated by the MRI machine. This alignment of the paramagnetic material's magnetic dipoles with the external magnetic field alters the magnetic properties of the surrounding tissues, allowing for the generation of high-resolution images that can be used to diagnose and monitor various medical conditions.

Related terms

Magnetic Susceptibility: A measure of the degree to which a material can be magnetized in an external magnetic field.

Magnetic Dipole: A pair of equal and opposite magnetic poles, representing the fundamental unit of magnetism.

Diamagnetism:

A type of magnetism where materials exhibit a weak negative magnetic susceptibility, meaning they are slightly repelled by an external magnetic field.