Magnetic materials and devices: Research and applications

Abstract

The history of magnetic materials dates back more than 2,500 years when the magnetic phenomenon was observed in lodestone, a naturally occurring mineral. At that time the only useful application of magnets was in compass needles. Since then, magnetic materials have found applications in a much wider domain. Their use in traditional areas such as electric motors, generators, loudspeakers, magnetic separators, etc. is well known. Lately they have found applications in more advanced fi elds such as biomedical imaging and drug delivery. However, the one fi eld that has probably been infl uenced the most is magnetic data storage technology. This technology has been advancing with almost the same pace as the semiconductor industry. A very exciting concept being explored is marrying semiconductor technology and the advanced magnetic data storage and processing technology. This emerging hybrid technology is known as spintronics. Spintronics utilizes the charge as well as the spin degrees of freedom of electrons. Further, spintronics requires the development of magnetic materials which can effi ciently inject spin polarized carriers into the semiconductors. Despite considerable efforts, effi cient injection of spins into nonmagnetic semiconductors continues to be a major hurdle in this fi eld. Conventional ferro-magnets such as Fe and Ni are not effi cient for the above application. This has led to an urgent need for developing new kinds of magnetic materials known as diluted magnetic semiconductors and