Spin valve multilayers

Fig. 5.3-22 (a) Schematic illustration of the spin valve multilayer originally proposed by Dieny et al. (15 nm NiFe/2.6 nm Cu/15 nm NiFe/10 nm FeMn). (b) Magnetization curve, and (c) relative change in resistance. The magnetic field is applied parallel to the exchange anisotropy (EA) field created by the FeMn layer. The current flows perpendicular to this direction. (After [3.100])... 

In conclusions, we believe that a use of FNF multilayer as a building block of SF spin valves opens an opportunity for effective control of magnitude and sign of Josephson junction critical current. Utilization of FNF multilayers also opens a way to engineering non Josephson spin valve devices. 

One problem of the application of GMR multilayer structures is that saturation magnetic fields are generally greater than 1000 Oe. Dieny etal. [141] eliminated this problem in 1991 by discovering the spin valve effect. They reported the GMR... 

Various approaches can be used to obtain a controlled alignment of the magnetization in magnetic multilayers. The most important material systems for devices are anti-ferromagnetic coupled multilayers and spin valves, which is discussed below. 

Figure 5.7.7 shows a typical MR curve for our spin-valve material. Because it contains only two active magnetic layers, the effect is much smaller than that in GMR multilayers, but the slope at zero field is much steeper and so is the sensitivity of the device. To increase the magnitude of the effect, the whole stack can be doubled or mirrored (dual spin valve) and reflecting nano-oxide layers (NOL) can be included. These act as mirrors for the conduction electrons, which are specularly reflected (spin conservative) back into the magnetic layer. With these measures, effects of greater than 20% can be obtained [30]. 

Besides the above multilayers and spin valves, other GMR-related material systems have been developed or are presently under investigation. 

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