hysteresikilvestä

Hysteresikilvestä refers to a phenomenon observed in certain materials, particularly in magnetic and ferroelectric contexts, where the state of the material depends not only on the current applied field but also on its past history. This means that as a field is increased and then decreased, the material's response does not retrace the same path. Instead, it forms a loop, known as a hysteresis loop.

In ferromagnetism, hysteresis refers to the relationship between the magnetic field strength (H) applied to a ferromagnetic material and its magnetic flux density (B) or magnetization (M). When an external magnetic field is applied, the magnetic domains within the material align. As the field is removed, some of this alignment persists, leading to remanence. To demagnetize the material completely, a reverse magnetic field (coercivity) must be applied. The area enclosed by the hysteresis loop represents energy loss, typically dissipated as heat, due to irreversible domain wall motion.

Similarly, in ferroelectrics, hysteresis is observed in the relationship between the applied electric field (E) and the electric polarization (P) or electric displacement (D). When an electric field is applied, the electric dipoles within the material align. Upon removal of the field, a remnant polarization remains. A reverse electric field is needed to reduce the polarization to zero (coercive field). This ferroelectric hysteresis is crucial for the operation of devices like non-volatile memory (FeRAM) and capacitors. The shape and size of the hysteresis loop provide important information about the material's properties, such as its coercivity, remanence, and energy loss.