. Magnetic materials continue to make significant advances in information processing, computation, and data storage. One of the most important characteristics of magnetic materials, and often a major limiting factor preventing further improvements, is the size of the magnetic moment. Any significant increase is recognized as an important achievement for magnetic applications that are ubiquitous in information technologies. Unfortunately, for nearly a century the maximum magnetic moment that can be achieved has only risen by a small amount. With this project, supported by the Solid State and Materials Chemistry program in NSF's Division of Materials Research, Prof. Idzerda and his research group explore a recently discovered group of magnetic alloys that show a remarkable 30% increase in the value of the maximum magnetic moment. Only by growing these magnetic alloys as a thin film of a specific crystal structure can these large moments be realized. Intriguingly, these alloys with these crystal structures are unstable in the bulk, explaining why these large magnetic moments were not observed until now. The increased depth of understanding of magnetism in thin films resulting from these studies is relevant to almost any technological applications that incorporate ultrathin magnetic films or multilayer hierarchies for magnetic recording, spin generation, spin manipulation and/or spin detection. The understanding of how growth of thin films that are not stable in the bulk, and the processes created during this project to generate these stable structures, can have an impact in other fields that rely on thin film structures. Examples include higher performance and better efficiencies in solar cells, the components leading to new battery breakthroughs, and advances in energy generation and storage materials. This project also provides training of undergraduate and graduate students in advanced vacuum deposition technology, film deposition methods, X-ray techniques, and electronic/magnetic characterization techniques, which have already been demonstrated to be excellent training for productive scientific careers in industrial, laboratory, and academic settings. Several Native American high school students from one of the seven Montana reservations are involved in this research through Prof. Idzerda's involvement in the Montana Apprenticeship Program (MAP).
establishment of high moment alloy films typically includes the incorporation of transition metal elements that have large moments. This project, supported by the Solid State and Materials Chemistry program in NSF's Division of Materials Research, characterizes the magnetic properties of bcc FeCo-based ternary alloys (FeCoMn and FeCoCr) to establish thin films with average magnetic moments significantly larger (>30%) than the Slater-Pauling limit value of 2.45 muB/atom. The magnetic moments and magnetic anisotropy are determined by vibrating-sample magnetometry, ferromagnetic resonance, and magnetic circular dichroism. The film compositions are determined from energy integrated X-ray absorption spectroscopy. An average atomic moment for an Fe10Co60Mn30 film with a moment of 3.25 muB/atom (as determined by XMCD) in a sparse sample data set of the compositional space for moment mapping has been observed previously, and this research builds on this exciting finding. In addition, the PI and his group investigate the mechanism for the observed Mn moment collapse with composition variation. Large magnetic moment materials are particularly important in high-density memory applications, spin torque hierarchies, BH-energy product device structures, control of spinor applications in nanoscale non-collinear magnets, and establishing enhanced electron spin-polarizations. Increasing the average atomic moment of these films can significantly improve their performance. In addition, epitaxial ultrathin films offer opportunities in spin-transport performance control through the modification of magnetic properties due to the reduced dimensionality and structural distortions created by film/lattice mismatches.
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.
