A ferrite is a type of ceramic compound composed of iron oxide (Fe 2 O 3 ) combined chemically with one or more additional metallicelements .  They are both electrically nonconductive and ferrimagnetic , meaning they can be magnetized or attracted to a magnet. Ferrites can be divided into two families based on their magnetic coercivity , their resistance to being demagnetized. Hard ferrites have high coercivity ; they are difficult to demagnetize. They are used to make magnets , for devices such as refrigerator magnets , loudspeakers and small electric motors . Soft ferrites have low coercivity . They are used in the electronics industry to make ferrite cores for inductors and transformers , and in various microwave components. Yogoro Kato and Takeshi Takei of the Tokyo Institute of Technology invented ferrite in 1930.