Giant Magnetoresistance

Topics: Magnetic field, Ferromagnetism, Giant magnetoresistance Pages: 2 (590 words) Published: February 25, 2013
In this essay we will explore some brief historical information about Giant Magnetoresistance (GMR), its basic principle of operation and some of its current and potential applications. To begin with, the idea of GMR is based on the change in the resistance of very thin (scale of nanometers) ferromagnetic materials when an external magnetic field is applied. The term “Giant” is to describe the size of the change in the resistivity in the order of 10% to 20%, considered to be enormous compared to the response of other magnetic sensors in the presence of an external magnetic field. Let us proceed with a historical overview, beginning from the original perception of the idea up to the creation of the first GMR materials. In 1936, Sir Neville Francis Mott first observed and explained the sudden increase of the resistivity in ferromagnetic metals when they are heated above the Curie temperature. Later in 1960’s, Albert Fert explained in his PhD thesis, at the University of Paris-Sud, how the resistivity of such metals depends on the spin of the carriers, namely up-spin and down-spin. But it was not until the 1980’s that the technology and experiments proved to be enough for the first creation of multilayered samples that exhibit Giant Magnetoresistance. During that period two different groups, Fert’s group and Peter Grunberg’s group, were involved in the creation of such materials by using the only available method at the time, which was Molecular Beam Epitaxy. Both Fert and Grunberg were awarded the Nobel prize at 2007 for their work on GMR. Moreover, allow me to explain the basic principles of operation of GMR in more detail. In a tri-layered sample for example (Fert), there are two ferromagnetic alloys that are separated by a very thin (nm) non-magnetic conductor. The separation distance, namely the width of the non-magnetic conductor has to be smaller than the mean free path of electrons in order to safely assume that scattering is...
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