Which description correctly defines paramagnetic materials?

Which description correctly defines paramagnetic materials?

• A. Align parallel to magnetic field lines, and do not retain magnetization after removal of the external field; lithium, magnesium
• B. All electrons are paired; align perpendicularly to magnetic field lines, and do not retain magnetic properties when the external field is removed
• C. Substances that can become magnetized; iron, nickel & cobalt
• D. Materials that have no magnetic response

Answer: (A)

Paramagnetic materials have unpaired electrons that give them tiny magnetic moments. When an external magnetic field is applied, these moments tend to line up with the field, producing a weak magnetization in the same direction as the field. Once the external field is removed, thermal motion randomizes the orientations and the material loses this magnetization. The description that a paramagnetic substance aligns with the field and does not retain magnetization after the field is gone captures this behavior. An example commonly cited is lithium, which is paramagnetic; magnesium is typically diamagnetic, which is a nuance to keep in mind, but the overall idea fits paramagnetism. This helps distinguish paramagnetic materials from ferromagnetic ones, which can become strongly magnetized and retain magnetization after the field is removed, and from materials with little or no magnetic response.

Paramagnetic materials have unpaired electrons that give them tiny magnetic moments. When an external magnetic field is applied, these moments tend to line up with the field, producing a weak magnetization in the same direction as the field. Once the external field is removed, thermal motion randomizes the orientations and the material loses this magnetization. The description that a paramagnetic substance aligns with the field and does not retain magnetization after the field is gone captures this behavior. An example commonly cited is lithium, which is paramagnetic; magnesium is typically diamagnetic, which is a nuance to keep in mind, but the overall idea fits paramagnetism. This helps distinguish paramagnetic materials from ferromagnetic ones, which can become strongly magnetized and retain magnetization after the field is removed, and from materials with little or no magnetic response.