Paramagnetism is a type of magnetism where materials exhibit a weak attraction to external magnetic fields. This behavior arises from the presence of unpaired electrons in the atoms or molecules of the material. Each unpaired electron has a magnetic moment due to its spin, which can align with an external magnetic field.
When a magnetic field is applied, these magnetic moments tend to align in the direction of the field, causing the material to become slightly magnetized. However, thermal motion tends to randomize the orientations, so the overall magnetization is relatively weak and temporary—it disappears once the external field is removed.
Characteristics of paramagnetic materials:
- They have positive magnetic susceptibility, though small.
- Their magnetism increases as temperature decreases, following Curie’s Law.
- Common examples include aluminum, platinum, and oxygen.
Paramagnetism is important in:
- Magnetic resonance imaging (MRI), where certain substances respond to magnetic fields,
- Chemical analysis, for determining the number of unpaired electrons in transition metal complexes,
- Material science, where understanding magnetic behavior guides the design of new devices.
Though subtle, paramagnetism provides key insights into the electronic structure and magnetic properties of atoms and molecules.