Antiferromagnetic interlayer exchange coupling in ferromagnetic GaMnAs/GaAs:Be multilayers

The interlayer exchange coupling (IEC) in magnetic multilayers determines the spin orientation of individual magnetic layers comprising the system. The dependence of the resistance on the resulting spin configuration in turn leads to the phenomenon known as giant magnetoresistance (GMR). [1] The GMR effect is of key importance to the area of spintronics, in which the spin degree of freedom is utilized in the operation of electronic devices. The behavior of IEC in metallic ferromagnetic multilayers has been extensively investigated, and the ability to control the IEC by structural parameters to be either ferromagnetic (FM) or antiferromagnetic (AFM) is now well established. In contrast, in multilayers consisting of FM semiconductors such as GaMnAs, the ability to change the IEC from FM to AFM is not well understood. Recently, however, AMF IEC was observed in GaMnAs/GaAs:Be multilayers [1]. These systems, however, show somewhat different behavior from their metallic counterparts. Specifically, the IEC in the GaMnAs/GaAs:Be multilayer system is observed to be long range, typically of over 10 nm, so that not only interactions between nearest neighbor (NN) layers of the multilayer, but also between next-nearest-neighbor (NNN) layers are involved during the magnetization reversal process. [2].