Theory of spin dependent reflection from interfaces

Magnetic multilayers, in which magnetic layers are separated by nonmagnetic spacer layers, exhibit many effects in which there has been significant recent interest: giant magnetoresistance (GMR), oscillatory exchange coupling, and spin-transfer torques. These effects are both of intrinsic scientific interest and of significant technological interest. For example, the giant magnetoresistance of nanometer thick magnetic layers is used in read heads for magnetic disk drives. Spin-dependent transmission and reflection probabilities, particularly those for Fermi surface electrons, play an important role in these effects.

First-principles calculations of transmission and reflection from Ag/Fe, Au/Fe, Cu/Co, Cu/Ni, and Cr/Fe interfaces all give results with strong enough spin dependence to explain much of the phenomena mentioned above. More details are provided on those pages.

Spin-dependent transmission probabilities for Au/Fe(001). The transmission probabilities are shown for various points on the Fermi surface projected onto the interface Brillouin zone. The color scale for the transmission probability is at the top. The top (bottom) two panels show the transmission for electrons incident from the Au (Fe) into the Fe (Au). The two right (left) panels show the transmission probabilities for the minority (majority) electrons. Au has only one sheet of states moving toward the interface, that sheet is shown in the whole interface Brillouin zone. For other interface orientations, or for complicated Fermi surfaces, the Fermi surface can have several sheets. That is, at some parallel wave vectors there are more than one state moving toward the interface. For the Fe Fermi surface, which has several sheets, each sheet is shown in a fraction of the Brillouin zone. The behavior over the full Fermi surface is found by rotating each sheet into each fraction of the Brillouin zone and stacking the sheets on top of each other.

Online: May 1996
Last Updated: February 2008

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