What is the property called hysteresis

That is what a transformer is - a magnetic flux is generated, which the Permalloy core uses to induce a current in another coil. This property, called hysteresis, causes energy losses in applications such as transformers. Therefore, "soft" magnetic materials with low hysteresis, such as silicon steel, are often used in the core, rather than "hard" magnetic materials used for permanent magnets. Soft iron cores increase the strength of the magnetic field inside the transformer.

Hence the eddy current losses. The core of a transformer is usually a full ring with two coils wrapped around it. One is connected to the power source and is called the "primary coil". The other powers the load and is called the "secondary coil". Soft magnetic materials and their associated devices (inductors, transformers, and motors) are often overlooked; however, they play a key role in the conversion of energy throughout the world.

The conversion of electrical power involves the bidirectional flow of energy between source, storage, and the grid, and is accomplished through the use of power electronics. Electric machines (motors and generators) convert mechanical energy into electrical energy and vice versa. The introduction of wide bandgap (WBG) semiconductors has enabled power conversion electronics and motor controllers to operate at relatively high frequencies. This reduces the size requirements for passive components (inductors and capacitors) in power electronics and enables higher-efficiency, higher-speed motors.

Several soft magnetic materials show promise for operation at high frequencies. As oxides, soft ferrites stand out from other magnetic materials because they are insulating and therefore good at reducing losses caused by eddy currents.