What is the Difference Between Paramagnetic and Superparamagnetic?

The main difference between paramagnetic and superparamagnetic materials lies in their magnetic susceptibility and the effect of particle size on their magnetism. Here are the key differences:

1. Magnetic Susceptibility: Paramagnetic materials have weak attractions to externally applied magnetic fields, and their magnetic susceptibility is generally smaller than that of superparamagnetic materials. Superparamagnetic materials, on the other hand, have a much larger magnetic susceptibility due to their small particle size.
2. Particle Size: Superparamagnetism occurs in small ferromagnetic or ferrimagnetic nanoparticles, typically less than a hundred nanometers in size. In these small nanoparticles, magnetization can randomly flip direction under the influence of temperature. Paramagnetism, however, can occur in materials with larger particle sizes.
3. Curie Temperature: Both paramagnetic and superparamagnetic materials can exhibit paramagnetic behavior, but the difference is that this usually occurs above the Curie temperature for paramagnetic materials, whereas it occurs below the Curie temperature for superparamagnetic materials.
4. Neel Relaxation Time: Superparamagnetic nanoparticles have a specific time between two flips of magnetization direction, called the Néel relaxation time. This time-dependent behavior is not typical for paramagnetic materials.

In summary, paramagnetic materials have weak attractions to magnetic fields and smaller magnetic susceptibility, while superparamagnetic materials have much larger magnetic susceptibility and are influenced by particle size and the Néel relaxation time.

Comparative Table: Paramagnetic vs Superparamagnetic

The main difference between paramagnetic and superparamagnetic materials lies in their magnetic susceptibility and the nature of their magnetization. Here is a table comparing the two types of materials:

In summary, paramagnetic materials have weak attractions to external magnetic fields and do not retain magnetization when the field is removed, while superparamagnetic materials have a larger magnetic susceptibility and display magnetization only when exposed to an external magnetic field. Superparamagnetism is a short-lived phenomenon that occurs in small ferromagnetic or ferrimagnetic nanoparticles.