Abstract
In this thesis, I study the magnetic response of a ferromagnet/DMS/ferromagnet junction. Linear response theory is used to calculate the magnetic susceptibility tensor. Because there is an internal magnetic ‾eld, namely magnetization, inside the DMS layer, it causes the tensor to have non-diagonal matrix elements. I attribute the non-diagonal elements to carrier spin precession under a uniform magnetic field. However, the Fermi gas owns an intrinsic magnetic response, RKKY exchange, so we call the non-diagonal elements spiral exchange. These two exchange mechanisms originate from each one's physical reason but interplay with each other in our system. The angle be- tween the two ferromagnetic layer moments, called the spiral angle, depends on the relative magnitude of the two exchange. This thesis emphasizes on studying how the sprial angle changes with magnetization, carrier spin lifetime, and width of the DMS layer. I will suggest that the spiral exchange can be possibly observed experimentally in the regime where carriers are partially polarized and have enough large spin relaxation rate.