Ionic liquids are liquid salts that are bringing rapid changes to the field of solid electronic materials. The implementation of ionic liquids in conjunction with these solid materials produces interfacial effects, especially when a bias is applied across the ionic liquid, forming an electric double layer. Electric double layers in ionic liquids are unique in their formation and the interfacial charges that are orders of magnitude higher than conventional techniques they can impart, providing new techniques for device design and implementation. In chapter 1, the fundamentals of the solid state electronic and magnetic materials are introduced, along with ionic liquids, and their essential properties that make them appropriate for use with solid films. Chapter 2 discusses the geometric impacts that should be taken into consideration when designing electric double layer devices, determining that the gate area to device area ratio plays the greatest role. Chapter 3 explores the application of electric double layer interfacial effects on ferroelectric lead zirconate- titanate films. The demonstrated large area switching, coupled with the minimal changes to film quality, and use on low quality films make this ionic liquid-solid interface an exciting proposition for future study and applications. Chapter 4 uses the same electric double layer to interrogate the ability to produce stoichiometry induced crystallographic transformations in strontium cobaltite family of films. Chapter 5 evaluates an antiferromagnetic lanthanum-strontium manganite that shows an unprecedented anisotropic magnetoresistance. These materials are excellent candidates for future spin based devices. The work discussed in this dissertation demonstrates a wide range of possible applications that can be affected by the use of ionic liquid solid interfaces, while also showing diversity in the types of studies and measurements that can be conducted by ionic liquids. Combining the electrostatic and electrochemical capabilities of ionic liquids with complex oxide films, the manipulation oxide properties can lead to advances in future electronic and magnetic properties and applications
