What is hysteresis?

Hysteresis refers to the delayed response of a system to a change in an external factor. In physics and materials science, hysteresis specifically relates to the phenomenon in which a physical system does not immediately and completely change to a new state when an external factor, such as magnetic field strength or temperature, is changed, but requires a certain amount of time to adjust.

Examples of hysteresis from physics

A well-known example of hysteresis is the behavior of ferromagnets. When a magnetic field is applied to a ferromagnet, the magnetic moments of the atoms of the material align with the field, resulting in a strong magnetisation. However, when the magnetic field is then switched off, the ferromagnet remains magnetized, in a state that corresponds to the original magnetic field. This means that a ferromagnet has a "memory" of which direction the magnetic field was last aligned to. Only when the magnetic field is changed strongly enough in the other direction is the ferromagnet completely demagnetized. An example of a ferromagnet is iron (Fe). It can be permanently magnetized and retains its magnetic force even without an external magnetic field.

Application examples of hysteresis in materials science and technology

Hysteresis is often utilized in materials science and technology to influence certain properties of materials. For example, the behavior of ferromagnets can be used in magnetic data storage to store information on hard disks or in magnetic tapes.

Where else can hysteresis be used?

The phenomenon of hysteresis is not only limited to the field of physics and materials science. There are also examples from other sciences, such as economics, where the behavior of markets and prices often exhibit hysteresis-like effects. In biology, hysteresis can also refer to the delayed response of biological systems to changes in environmental conditions, such as the behavior of populations to changes in habitat and food supply.