**Abstract**

Functional magnetic materials, also called the smart materials of the future, are a group of materials having important and interesting physical properties, which can be affected when an external magnetic field is applied. They are intriguing models that have a strong impact on improving different technologies. Their magnetic response to an external magnetic field can be represented as paramagnetic, diamagnetic, ferromagnetic, or antiferromagnetic. Compared with bulk materials, they show uncommon magnetic behavior as a result of their surface/ interface effects, electronic charge transfer, and magnetic interactions. They can be used in different vital applications like data storage systems, refrigeration, magnetic recording, and medical studies. In this chapter, essential attractive magnetic properties that are relevant to different applications will be explained.

**Keywords:** functional materials, magnetic nanoparticles, magnetic field, physical properties, applications
