Magnetic garnet thin films: novel properties through interface and site occupancy engineering

NON-TECHNICAL SUMMARY Iron garnets are a class of oxide material with a wide range of useful magnetic properties, making them candidates for next generation solid-state memory and logic devices in which data is stored and manipulated by changing the magnetization direction of the garnet. The development of processes to grow thin films of iron garnets has led to an explosion of interest, but the great majority of this work involves single layer garnet films of simple compositions. This leaves several interesting questions unanswered, which form the core of this proposal. First, the proposal will address what magnetic properties can emerge from a multilayer garnet film made up of layers of different composition each a few atoms thick. Second, whether the type of atoms in the crystal can be controlled and arranged on the atomic scale, and what magnetic properties emerge from this ordering. An intriguing third question is whether iron garnets, which are naturally insulators, can be grown with electrical conductivity, which would facilitate electrical reading and writing of a data storage device made of garnet. The technical findings and the new material capabilities developed in this project will contribute to the development of magnetic memory, logic and other thin film devices and will be published and communicated to industrial researchers. Graduate and undergraduate students, including from a local community college, will be trained in materials design, growth and characterization. Results from the research will be incorporated into coursework and free online subjects, a public outreach activity, and into summer programs designed to increase diversity. TECHNICAL SUMMARY Engineering of site occupancy and interfaces in oxide heterostructures presents a tremendous opportunity to manipulate the properties of complex oxide thin films and to reveal new thin film phenomena. However, most work on oxide heterostructures has focused on perovskites, and there is little work on garnet oxide heterostructures. This proposal develops thin film magnetic garnet superlattices, garnet films with ordering of two or more rare earth cations within the unit cell, and conductive garnet films. These thin film structures will facilitate the introduction of electrically-controlled magnetic properties, multiferroic stacks, charge and ion conduction pathways, and new magnetic behavior promoted by symmetry breaking. The new material capabilities could form the basis of magnetic memory, logic and other thin film devices. Broader impacts include training of graduate and undergraduate students, industrial and public outreach, online teaching, and participation in summer programs designed to increase diversity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.