Magnetic multilayer device

Myers EB, Ralph DC, Katine JA, Louie RN, Buhrman RA (1999) Current-induced switching of domains in magnetic multilayer devices. Science 285 867-870... 

There has been a recent upsurge of interest in electrochemical deposition, due mainly to three new technologies (1) metal deposition for the fabrication of integrated circuits, (2) deposition for magnetic recording devices (heads, disks), and (3) deposition of multilayer structures. 

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. 

Initial wavelength selection is done by a mechanical (rotating) velocity selector, since energy resolution is not an important issue here. Polarized neutrons may be produced by reflection by a magnetic multilayer mirror. Essential parts are the so-called flippers. These devices, consisting of flat coils, can change the direction of the neutron spin (which is extremely sensitive to external magnetic fields). 

Kymissis et al. have examined the possibility of generation of electrical power parasitically from devices built in a shoe, a wearable subsystem for the soldier. Merits of three different types of piezoelectric devices are compared. They are a unimorph strip piezoceramic composite, a stave of multilayer laminate of PVDF foil, and a shoe-mounted rotary magnetic generator as a part of technology demonstration a piezoelectric embedded shoe has also been postulated to periodically broadcast a digital radio frequency identification (RFID) signal as the wearer walks. 

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]. 

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