Magnetic Materials and Permanent Magnets

Magnetic materials are those that exhibit some form of magnetism when subjected to magnetic fields. They can possess properties that make their magnetization persistent even after exposure to strong external fields has been removed. This is where the concept of magnetic domains comes into play. A domain is an area within which all atomic dipoles point in approximately the same direction. These areas do not necessarily align with each other; instead, they align along the path of least resistance. When a material is brought near another magnetic field, its own internal structure often changes to allow it to line up better with the new field.

Permanent magnets have attracted considerable attention due to their usefulness. Permanent magnets come from two basic types of magnetic materials: ferromagnetism and ferrimagnetism. Materials such as iron, nickel, cobalt, and manganese exhibit ferromagnetism while a combination of rare earth metals like neodymium and samarium exhibits ferrimagnetism.

Magnets consist primarily of clusters of small, tightly packed particles, called Weiss domains, named after Pierre Curie's colleague Paul Weiss, who first discovered them. Each Weiss domain is composed of many tiny individual atoms whose magnetic moments align themselves in one direction, forming a miniature bar magnet.

The main purpose of using magnetic materials lies in the ability of these materials to retain their magnetic state when removed from a magnetic field, as well as being able to create their own magnetic fields. Today, many technologies rely on the principles of magnetic materials. For example, tapes used by data storage systems store information via magnetic polarity change. In electronics manufacturing, transformers use magnetic cores made of soft magnetic materials to step down high voltage direct current supplies.