In this section we will present the analysis, in the framework of
dynamical systems theory, of some relevant technological
applications connected with magnetic recording devices. In
particular, we will focus our attention on magnetization reversal
processes, commonly referred to as magnetization switching
processes. Basically, if we assume that initially the
magnetization is aligned in the positive easy axis direction (for
example corresponding to the bit value 0), the switching problem
consists in manipulating the control variables in order to drive
definitely magnetization into the opposite orientation (bit 1). At
present time, there are more than one way to achieve switching.
The conventional way obtains the switching by using magnetic field
produced by external currents, and this technique is mostly used
in hard disks realizations. Recently, the possibility of using
spin-polarized currents, injected directly into the ferromagnetic
medium, has been investigated both experimentally and
theoretically. This way to control switching has considerable
applications in MRAMs technology, since in this way it is possible
to circumvent the difficulty of generating magnetic fields that
switch only the target cell. The spin-polarized current driven
switching will be analyzed in section 2.6.
Subsections
