Even though flash type memory is a convenient technology for cheap bulk memory and is gradually replacing conventional magnetic storage type memory (e.g. hard disks), the ever increasing demand for bigger and cheaper bulk memory, and thus the need for scaling, will outrun the capabilities of flash type based memory soon.
In search for a promising replacement one has to define which properties an ideal (universal) memory has to exhibit in order to fulfill its application. An ideal memory should unify several properties, like high endurance of the stored information, low power for writing and reading, fast switching and access, no or almost no wear due to reading/writing cycles, long retention times, etc. The exploration of spin as an available degree of freedom will be the next logical step towards future memory. In order to store, read or write information via spin orientation, magnetic materials and device structures including these are needed. These demands in combination with scaling will lead to the introduction of new materials, e.g. ferroelectrics, magnetic semiconductors, antiferromagnets in microelectronics, etc. Furthermore, spin based technology allows not only the manufacture of memory and logic devices, it also enables the combination of information storage and data procession in a single device and hence fully nonvolatile information processing systems.
Micromagnetic theory based on the Landau-Lifshitz-Gilbert (LLG) equation enables the simulation of magnetic materials as well as devices in order to analyze their properties and ways to optimize them. The microscopic magnetic field entering the LLG equation is computed from the total Gibbs free energy, which describes the physics of a micromagnetic system. It consists of several energy contributions like exchange energy, magnetocrystalline anisotropy energy, magnetostrictive/magnetoelastic energy, and magnetostatic energy.
The presented figure illustrates a magnetocrystalline cubic anisotropy term plotted as a function of azimuthal and polar angle. Micromagnetic simulations must describe several newly discovered effects, such as spin transfer torque, current induced domain wall motion, Tunnel MagnetoResistance (TMR), Tunnel Anisotropic MagnetoResistance (TAMR). Despite the great progress recently achieved, further research has to be carried out to overcome technological and physical hurdles in fabricating new devices.