Mechanical detection of nuclear spin relaxation in a micron-size crystal

A room temperature nuclear magnetic resonance force microscope (MRFM), fitted in a 1Tesla electromagnet, is used to measure the nuclear spin relaxation of H in a micron-size (70ng) crystal of ammonium sulfate. NMR sequences, combining both pulsed and continuous wave r.f. fields, have allowed us to measure mechanically T2 and T1, the transverse and longitudinal spin relaxation times. Because two spin species with different T1 values are measured in our 7μm thick crystal, magnetic resonance imaging of their spatial distribution inside the sample section are performed. To understand quantitatively the measured signal, we carefully study the influence of the spin-lattice relaxation and the non-adiabaticity of the c.w. sequence on the intensity and time dependence of the detected signal. PACS. 07.79.Pk Magnetic force microscopes – 76.60.-k Nuclear magnetic resonance and relaxation – 87.61.Ff Magnetic resonance imaging: Instrumentation