Superparamagnetism is a phenomenon observed in small ferromagnetic or ferrimagnetic nanoparticles, where they exhibit magnetic properties only in the presence of an external magnetic field, losing their magnetization once the field is removed. This occurs because thermal fluctuations are sufficient to randomize the direction of magnetization, making them behave like paramagnetic materials despite having a high magnetic susceptibility.

Superparamagnetism

Ferromagnetic nanoparticles

ferrimagnetic nanoparticles

Magnetic properties refer to the behavior of materials in response to magnetic fields, which is determined by the alignment of atomic magnetic moments. These properties are crucial in applications ranging from data storage to medical imaging, and they vary widely among materials, leading to classifications such as ferromagnetic, paramagnetic, and diamagnetic.

magnetic properties

An external magnetic field is a magnetic field that is applied to a system from an outside source, influencing the magnetic properties and behavior of materials within the field. This can affect phenomena such as magnetic resonance, magnetization, and electromagnetic induction, playing a critical role in various scientific and industrial applications.

external magnetic field

Magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. It is a measure of how much a material will become magnetized in an external magnetic field and is crucial in determining the magnetic properties of materials.

magnetization

Thermal fluctuations are random variations in physical quantities due to thermal energy, which become significant at microscopic scales and affect the stability and behavior of systems. These fluctuations play a crucial role in processes like phase transitions, chemical reactions, and biological functions at the molecular level.

thermal fluctuations

direction of magnetization

Paramagnetic materials are substances that are weakly attracted to an external magnetic field due to the presence of unpaired electrons in their atoms or molecules. Unlike ferromagnetic materials, their magnetization is transient and occurs only in the presence of an applied magnetic field, disappearing once the field is removed.

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