Iron and iron oxides
Iron (chemical symbol Fe, Latin: ferrum) is one of the most important metals in everyday use. Steel girders for bridges and houses, rolled plates made of iron and steel, i.e. for the construction of automobiles, screws and nails - all these consist of iron or of steel, the refined form of iron.
Iron is one of the most abundant metals on earth.
It is mined as iron ore in the form of iron oxides. Chemically, these iron oxides are Fe2O3, Fe3O4 or very rarely FeO. In 2000 about half a billion tons of iron were manufactured from iron ore and this number is increasing.
First the mined iron ore has to be extracted from its oxidic form to the elemental, the metallic iron. For this purpose there exist huge blast-furnaces  that reduce iron oxide chemically to iron, in most cases with the help of coal. Depending on its intended use the iron is then processed to structural or tool steel by adding more metals or by reducing the carbon content.
Ferrous metal and (certain) iron oxides are magnetic, in the past they were used e.g. on audio tapes and on cassettes to store sound recordings, today this is only a niche area in audio engineering. Later on, such iron compounds were also used on (floppy) disks until they, in turn, were almost completely replaced by CDs, DVDs, and storage sticks. However, magnetic recording media is still used in hard drives of computers. With the increased emergence of PCs as home computers and media servers, whose storage capacities are provided by hard drives, one could speak of a renaissance of magnetic recording for the personal music collection.
Apart from iron, cobalt and nickel are also used for modern hard drives  that use the Giant Magneto Resistance Effect (GMR ) as a base for data recording. Structures of just a few nanometers in size are used here to store the data and it is only these extremely small structures that make it possible today (in 2009) to store data in the range of terabytes on hard drives. Iron oxide is also used as a colour pigment with the typical rust-red colour. Because of its high chemical stability iron oxide is extremely durable as a dye; it can already be seen in antique paintings.
But iron oxide can be undesired as well: oxidation of iron makes for the biggest problem in dealing with this material, as this kind of oxidation is known in everyday life as “rusting”. This process costs the world economy billions each year, because when it rusts, iron looses its mechanical stability and crumbles to small pieces of rust.
Iron is prevalent in the living nature as well, as part of the haemoglobin of our red blood cells it plays as important a role for higher organisms as in the enzyme nitrogenise that accomplishes self-fertilization in some plants. Without iron humans and plants would not be viable. Patients with the so-called “anaemia” are treated with doses of iron salt to support the formation of haemoglobin.
Some newer diagnostic procedures most of them still in a test phase, use nano iron oxide as a contrast medium for medical imaging processes. Such magnetic processes shall - whenever possible - reduce the radiation exposure in medical examinations.
Fe oxide nanoparticles promise
progress in cancer therapy. (Hyperthermia)