1. Scanned-probe detection of electron spin resonance from a nitroxide spin probe
- Author
-
Peter P. Borbat, Steven A. Hickman, Sarah J Wright, SangGap Lee, Eric W. Moore, Jack H. Freed, Lee E. Harrell, and John A. Marohn
- Subjects
Multidisciplinary ,Cantilever ,Magnetic Resonance Spectroscopy ,Spin polarization ,Molecular Structure ,Chemistry ,Electron Spin Resonance Spectroscopy ,Magnetic resonance force microscopy ,Equipment Design ,Zero field splitting ,Ferromagnetic resonance ,Molecular physics ,Biophysical Phenomena ,law.invention ,Computer Science::Other ,Spin probe ,Cyclic N-Oxides ,Nuclear magnetic resonance ,law ,Physical Sciences ,Spin echo ,Thermodynamics ,Spin Labels ,Electron paramagnetic resonance ,Microwaves - Abstract
We report an approach that extends the applicability of ultrasensitive force-gradient detection of magnetic resonance to samples with spin-lattice relaxation times ( T 1 ) as short as a single cantilever period. To demonstrate the generality of the approach, which relies on detecting either cantilever frequency or phase, we used it to detect electron spin resonance from a T 1 = 1 ms nitroxide spin probe in a thin film at 4.2 K and 0.6 T. By using a custom-fabricated cantilever with a 4 μ m -diameter nickel tip, we achieve a magnetic resonance sensitivity of 400 Bohr magnetons in a 1 Hz bandwidth. A theory is presented that quantitatively predicts both the lineshape and the magnitude of the observed cantilever frequency shift as a function of field and cantilever-sample separation. Good agreement was found between nitroxide T 1 's measured mechanically and inductively, indicating that the cantilever magnet is not an appreciable source of spin-lattice relaxation here. We suggest that the new approach has a number of advantages that make it well suited to push magnetic resonance detection and imaging of nitroxide spin labels in an individual macromolecule to single-spin sensitivity.
- Published
- 2009