Control of Interfaces in Magnetic Tunnel Junctions

Magnetic tunnel junctions, or MTJs, have been an important nanodevice in spintronics and applications. A number of MTJ parameters have been studied and explored in detail in an attempt to fully understand and better control these devices. With this, MTJs have been made increasingly complex over the years, with an increasing number of layers, and layers with various chemical properties. Here, the focus with MTJs, is analyzing and minimizing the energy of operation and switching, so the complex junctions were foregone in favor of the traditional trilayer designs. One key step in controlling the energy needed to operate these junctions is exploring changes in the surface geometries of these layers. Breaking symmetry at the surface of the crystal structures in ferromagnetic layers contributes to changes in the magnetic anisotropy of the layers. Because of this, the change in anisotropy leads to a change in the required switching energy for the junction, which we demonstrate in this work. While many materials can be used for the layers in the MTJs, the samples explored were FeCo, MgO and Fe layers. As a result of this these trilayer junctions have a magnetoresistance from 60% to 200%.