Ferromagnetic Resonance Force Microscopy

Spin pumping, the transfer of spin angular momentum from the resonantly driven magnetization of a ferromagnet into an adjacent material, represents an intriguing phenomenon with potentially significant technological importance. Scanned probe magnetic resonance is a powerful tool in this context offering high resolution magnetic resonance imaging, localized spin excitation and direct measurement of spin relaxation and damping. Because it is based on direct detection of the dipole interaction between a micromagnetic probe and the ensemble of spins under study, it is applicable to a broad variety of spin-containing materials, and deeply buried regions can be imaged. Here we report on microscopic scanned probe magnetic resonance studies of spin dynamics, and explore the relationships between spin lifetime and transport. Electron spin resonance measurements of nanostructured volumes of diamond containing nitrogen impurities reveal an unexpected sensitivity of spin dynamics to confinement of the volume under study. Scanned probe ferromagnetic resonance imaging (FMRI) is a novel magnetic imaging technique based on Magnetic Resonance Force Microscopy that offers the ability to image nanoscale properties of buried ferromagnets. Able to map internal fields with spectroscopic precision, FMRI offers a unique approach to the study of dynamics of microscopic ferromagnets and localized spin waves. This work was performed in collaboration J. Cardellino, N. Scozzaro, I. Lee, M. Herman, C. Du, H. Wang, R. Adur, A. Berger, D. Pelekhov and F.Y. Yang. We acknowledge support by the U.S. DOE through Grant No. DE-FG02-03ER46054, by the NSF through Grant No. 0820414 and by the Army Research Office through Grant W911NF0910147.