Ferromagnetic layers

Researchers found that within picoseconds of absorbing an ultrashort laser pulse, electron spins in a semiconductor (GaAs) spontaneously polarize along the magnetization of a thin ferromagnetic layer, such as Iron (Fe), deposited on top of the GaAs. 

Now, suppose one ferromagnetic layer has a majority of spin up electrons. If the next layer also has a majority of spin up electrons (Figure 9.12(a)), then current can flow readily from one ferromagnetic layer to the next. However, if the next layer has a majority of spin down electrons (Figure 9.12(b)), then the current from the... 

In hard disk read heads, one ferromagnetic layer has its spin orientation fixed by coupling to an antiferromagnetic layer (Figure 9.13). A second ferromagnetic layer separated from the first by a nonmagnetic metal, is free to change its spin orientation when a field is applied. 

FIGURE 9.13 Two ferromagnetic layers, as in a magnetic hard disk read head, illustrating pinning hy an antiferromagnetic layer. 

Here, a is the angle between the magnetisation directions of the two ferromagnetic layers which form the spin-valve. 

In order to get a better understanding of the properties of the superconducting condensate in the presence of the ferromagnetic layers, we consider in this section a simple case of a trilayered F/S/F structure (see Fig. 1). Generalization to a multilayered structures is of no difficulties and will be done in the next section. 

Mnlr based synthetic antiferromagnet spin valve [27]. These SAF structures have another advantage. Since the effective moment of the pinned layer is low (Meff = M - M2, where M is the moment of each ferromagnetic layer), its contribution to the demagnetizing and coupling fields acting on the free layer is much weaker than in conventional spin valves. Similar SAF structures can be used as synthetic free layers (SF), in order to reduce the effective magnetic thickness and moment of the free layer [28, 29],... 

For a comparison of the magnetic field sensitivity of the SVT and MTT with that of other spintronic devices it is illustrative to define the hot-electron transmission polarization of a ferromagnetic layer as... 

The magnetocurrent of SVT and MTT devices can be written in terms of the transmission polarization of the two ferromagnetic layers [149], as previously described in Eq.14,... 

The structure of KCrF3 is derived from the perovskite structure by a tetragonal distortion4. An antiferrodistortive coupling occurs between half-filled dz orbitals and empty d 2 yj orbitals. The superexchange interaction d°z y2 - p - dz2 leads to ferromagnetic layers, antiferromagnetically bound via the empty dx2 y2 orbitals. 

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