Use of Nuclear Spin Noise Spectroscopy to Monitor Slow Magnetization Buildup at Millikelvin Temperatures.
At ultralow temperatures, longitudinal nuclear magnetic relaxation times become exceedingly long and spectral lines are very broad. These facts pose particular challenges for the measurement of NMR spectra and spin relaxation phenomena. Nuclear spin noise spectroscopy is used to monitor proton spin polarization buildup to thermal equilibrium of a mixture of glycerol, water, and copper oxide nanoparticles at 17.5 mK in a static magnetic field of 2.5 T. Relaxation times determined in such a way are essentially free from perturbations caused by excitation radiofrequency pulses, radiation damping, and insufficient excitation bandwidth. The experimental spin-lattice relaxation times determined on resonance by saturation recovery with spin noise detection are consistently longer than those determined by using pulse excitation. These longer values are in better accordance with the expected field dependence trend than those obtained by on-resonance experiments with pulsed excitation.
Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria.
Maria Theresia
MT
Pöschko
School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.|64 Canterbury road, Penn, Wolverhampton, WV4 4EH, UK.
David
D
Peat
School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
John
J
Owers-Bradley
Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040, Linz, Austria. norbert.mueller@jku.at.|Faculty of Science, University of South Bohemia, Branišovská 1645/31A, 370 05, České Budějovice, Czech Republic. norbert.mueller@jku.at.
Norbert
http://orcid.org/0000-0002-7621-3980
N
Müller
NMR spectroscopy; magnetic properties; nanoparticles; radiation damping; spin relaxation