Tunnel Magnetoresistance in MgO-Based Magnetic Tunnel Junctions


Authored by: Shinji Yuasa

Spintronics Handbook: Spin Transport and Magnetism, Second Edition

Print publication date:  May  2019
Online publication date:  May  2019

Print ISBN: 9781498769525
eBook ISBN: 9780429423079
Adobe ISBN:


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A magnetic tunnel junction (MTJ) consists of an ultra-thin insulating layer (tunnel barrier) sandwiched between two ferromagnetic (FM) metal layers (electrodes), as shown in Figure 12.1a. The resistance of MTJ depends on the relative magnetic alignment (parallel or antiparallel) of the electrodes. The tunnel resistance, R, of MTJ, is lower when the magnetizations are parallel than it is when the magnetizations are antiparallel, as shown in Figure 12.1b. That is, R P < R AP. This change in resistance with the relative orientation of the two magnetic layers, called the tunnel magnetoresistance (TMR) effect, is one of the most important phenomena in spintronics. The size of this effect is measured by the fractional change in resistance (R APR P)/R P × 100(%), which is called the magnetoresistance (MR) ratio. The MR ratio at room temperature (RT) and a low magnetic field (typically < 10 mT) represent a performance index for industrial applications. Figure 12.1 (a) Typical cross-sectional structure of magnetic tunnel junction (MTJ) with spin-valve structure. (b) Typical magnetoresistance curve of spin-valve-type MTJ and definition of magnetoresistance (MR) ratio.

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