In magnetic multilayers, the spin polarized currents flowing between the magnetic layers can exert torques on the magnetizations of the layers when the magnetizations are not collinear. The theory of these spin transfer torques is developed in terms of semiclassical transport calculations coupled with quantum mechanical calculations of the behavior of spins at interfaces. The result is an expression for the torque in terms of the geometry of the devices and the magnetic configuration.
Handbook of Magnetism and Advanced Magnetic Materials, Vol. 2
Theory of Spin Transfer Torque, Handbook of Magnetism and Advanced Magnetic Materials, Vol. 2, Wiley, Hoboken, NJ, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=620597
(Accessed May 28, 2023)