title: Magnetic Resonance Force Microscopy Detected Long-Lived Spin Magnetization.
abstract: Magnetic resonance force microscopy (MRFM), which combines magnetic resonance imaging with scanning probe microscopy together, is capable of performing ultra-sensitive detection of spin magnetization. In an attempt to observe dynamic nuclear polarization (DNP) in an MRFM experiment, which could possibly further improve its sensitivity towards a single proton spin, a film of perdeuterated polystyrene doped with a nitroxide electron-spin probe was prepared. A high-compliance cantilever with a 4μm diameter magnetic tip was brought near the film at a temperature of 7.3 K and in a background magnetic field of ~0.6 T. The film was irradiated with 16.7 GHz microwaves while the resulting transient change in cantilever frequency was recorded in real time. In addition to observing the expected prompt change in cantilever frequency due to saturation of the nitroxide's electron-spin magnetization, we observed a persistent cantilever frequency change. Based on its magnitude, lifetime, and field dependence, we tentatively attribute the persistent signal to polarized deuteron magnetization createdviatransfer of magnetization from electron spins. Further measurements of the persistent signal's dependence on the cantilever amplitude and tip-sample separation are presented and explained by the cross-effect DNP mechanism in high magnetic field gradients.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301.
authors.forename: Jonilyn G
authors.initials: JG
authors.lastname: Longenecker
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301.
authors.forename: Eric W
authors.initials: EW
authors.lastname: Moore
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301.
authors.forename: John A
authors.initials: JA
authors.lastname: Marohn