Hexagonal Ferrites: From Fridge Magnets to High Tech Uses

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Hexagonal ferrites have a hexagonal crystal structure. Photo by Dr. Bestione

Hexagonal ferrite ceramics have well-known abilities and properties, and are used in everything from magnetic notepads on your fridge to high-tech applications. Now, scientists have discovered room-temperature multiferroic hexaferrites, which extends the capabilities of these magnets tremendously.

Hexagonal Ferrites: What Are They?

Hexagonal ferrites, also known as hexaferrites, are magnetic iron oxides with a hexagonal structure. They are formed by iron (Fe), oxygen (O) and one or more other atoms, which could be barium (Ba), strontium (Sr), cobalt (Co) or a combination of these.

Although the name may not mean anything to most people, hexagonal ferrites one of the most common and useful materials, due to their magnetic properties.

From Natural Magnets to Synthetic Magnetic Ferrites

The developments of hexagonal ferrites started in the 1950s – this is when scientists studied and tried to reproduce the structure of magnetoplumbite, a natural magnetic mineral.

Magnetoplumbite is the combination of two oxides, lead oxide (PbO) and iron oxide (Fe2O3).

In the synthetic hexagonal ferrites, lead is replaced by barium or strontium, the simplest example being BaFe12O19.

As implied by their name, hexagonal ferrites have a hexagonal crystal structure, as shown in the picture above.

Hexaferrites: The Most Common Magnetic Material

Hexagonal ferrites are the most common magnetic materials used today, covering about 90% of the market – and it’s a big market: in 2012, it was worth more than 3 billion dollars. According to recent data, about 300,000 tonnes of hexagonal ferrites are produced every year; this corresponds to 50 g for every person on earth.

The wide spread use of ferrite magnets is due to their lower cost compared to other magnets, such as metallic alloys, the best of which are based on the expensive rare earth metal neodymium.

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