Editing Magnetic core (section)

==== Carbonyl iron ====
{{main article|carbonyl iron}}

Powdered cores made of [[carbonyl iron]], a highly pure iron, have high stability of parameters across a wide range of [[temperature]]s and [[magnetic flux]] levels, with excellent [[Q factor]]s between 50&nbsp;kHz and 200&nbsp;MHz. Carbonyl iron powders are basically constituted of micrometer-size [[sphere]]s of iron coated in a thin layer of [[electrical insulation]]. This is equivalent to a microscopic laminated magnetic circuit (see silicon steel, above), hence reducing the [[eddy currents]], particularly at very high frequencies. Carbonyl iron has lower losses than hydrogen-reduced iron, but also lower permeability.

A popular application of carbonyl iron-based magnetic cores is in high-frequency and broadband [[inductor]]s and [[transformer]]s, especially higher power ones.

Carbonyl iron cores are often called "RF cores".

The as-prepared particles, "E-type"and have onion-like skin, with concentric shells separated with a gap. They contain significant amount of carbon. They behave as much smaller than what their outer size would suggest. The "C-type" particles can be prepared by heating the E-type ones in hydrogen atmosphere at 400&nbsp;°C for prolonged time, resulting in carbon-free powders.<ref name="handbkferr"/>