UC Berkeley

This thesis presents the study of magnetoelectricity in artificial multiferroic heterostructures, focussing on the FeRh metamagnetic phase transition. Spin based electronic systems are ideal for many applications, primarily as a result of long term stability. Toward this goal, there is a need for electrically modifiable and differentiable magnetic states. First, new methodologies to determine and control the antiferromagnetic axis in the low temperature antiferromagnetic phase of FeRh are considered. Second, In an effort to increase the ability to control magnetism with an applied electric field through the converse magnetoelectric effect, FeRh is combined with piezoelectric materials. In association with the large volumetric magnetostriction coefficient of FeRh, a composite multiferroic with the largest magnetoelectric coupling is observed. Finally, the out-of-plane magnetic anisotropy is investigated as a function of the ferromagnetic phase fraction and epitaxial strain. This is applied toward investigation of zero magnetic field magnetoelectric control of the magnetic phase and the apparent memory of the magnetization direction across repeated phase reversal.