Theory of Spin-polarized Current and Spin-transfer Torque in Magnetic Multilayers

Author(s):  
John Slonczewski
Author(s):  
T. Kimura

This chapter discusses the spin-transfer effect, which is described as the transfer of the spin angular momentum between the conduction electrons and the magnetization of the ferromagnet that occurs due to the conservation of the spin angular momentum. L. Berger, who introduced the concept in 1984, considered the exchange interaction between the conduction electron and the localized magnetic moment, and predicted that a magnetic domain wall can be moved by flowing the spin current. The spin-transfer effect was brought into the limelight by the progress in microfabrication techniques and the discovery of the giant magnetoresistance effect in magnetic multilayers. Berger, at the same time, separately studied the spin-transfer torque in a system similar to Slonczewski’s magnetic multilayered system and predicted spontaneous magnetization precession.


2007 ◽  
Vol 19 (16) ◽  
pp. 165212 ◽  
Author(s):  
A Manchon ◽  
N Ryzhanova ◽  
N Strelkov ◽  
A Vedyayev ◽  
B Dieny

SPIN ◽  
2020 ◽  
Vol 10 (02) ◽  
pp. 2050012
Author(s):  
H. Bhoomeeswaran ◽  
P. Sabareesan

The current-driven magnetization precession dynamics stimulated by Spin-Transfer Torque (STT) in a trilayer spin-valve device (typically Spin-Torque Nanooscillator (STNO)) is numerically investigated by solving the Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation. We have devised four STNO devices made of ferromagnetic alloys such as CoPt, CoFeB, Fe[Formula: see text]B[Formula: see text]Ni2 and EuO, which act as free and fixed layers. Here, copper acts as a nonmagnetic spacer for all the devices. In this work, we have introduced the current-induced Oersted field, which is generated when a spin-polarized current passes through the device. The generated Oersted field strength is varied by increasing the diameter of the STNO device. Frequency tunability is achieved in all the four devices, whereas the power of the individual device reduces. The frequency and power of the devices depend entirely on the saturation magnetization of the material, which inherently reflects in the current density and the coherence of the spin-polarized DC. In all devices, the frequency increases, whereas the power decreases by increasing the strength of the Oersted field. Among the four devices, the maximum frequency can be tuned up to 104[Formula: see text]GHz with 40[Formula: see text]nm device diameter, which is obtained for EuO material. This opens a promising source and paves a glittering future for the nanoscale spintronic devices.


2020 ◽  
Vol 532 (3) ◽  
pp. 1900357
Author(s):  
Rodrigo Turcati ◽  
Carlos Andres Bonilla Quintero ◽  
José Abdalla Helayël‐Neto ◽  
Enrique Arias

Author(s):  
K. Takanashi ◽  
Y. Sakuraba

This chapter explains how the exchange splitting between up- and down-spin bands in ferromagnets unexceptionally generates spin-polarized electronic states at the Fermi energy. The quantity of spin polarization P in ferromagnets is one of the important parameters for application in spintronics, since a ferromagnet having a higher P is able to generate larger various spin-dependent effects such as the magnetoresistance effect, spin transfer torque, spin accumulation, and so on. However, the spin polarizations of general 3d transition metals or alloys generally limit the size of spin-dependent effects. Thus,“‘half-metals” attract much interest as an ideal source of spin current and spin-dependent scattering because they possess perfectly spin-polarized conduction electrons due to the energy band gap in either the up- or down-spin channel at the Fermi level.


2010 ◽  
Vol 46 (6) ◽  
pp. 1580-1583
Author(s):  
Nyuk Leong Chung ◽  
Mansoor B. A. Jalil ◽  
Seng Ghee Tan

2007 ◽  
Vol 43 (4) ◽  
pp. 1677-1680 ◽  
Author(s):  
M. Carpentieri ◽  
G. Consolo ◽  
B. Azzerboni ◽  
L. Torres ◽  
E. Cardelli

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