Ferrite circulators are radio-frequency circulators which are composed of magnetized ferrite materials. Ferrite loop antennas are made by winding fine wire around a ferrite rod. Current technologies include dielectric composites and metal fibers containing ferrite isotopes. Toroidal core coils are manufactured of various materials, primarily ferrite, powdered iron and laminated cores. For higher frequencies, inductors are made with cores of ferrite. Between the disks is a ferrite toroid. They often have toroidal ferrite cores. Iron oxide and barium or strontium carbonate are used in manufacturing of hard ferrite magnets. The magnet in headphones is typically composed of ferrite or neodymium. Strontium carbonate is used in the manufacturing of hard ferrite magnets. It has a higher saturation magnetization than the ferrite magnets. Hyperthermia treatment involves implanting a bioceramic material that contains a ferrite or other magnetic material. It can also be built from magnetic material such as ferrite cores or magnetic bubbles. Materials systems studied included cobalt ferrite, magnetite, SrTiO3, BaTiO3, PMNT. Almost all planar transformers use a ferrite planar core.