NMR shifts in 3He in aerogel induced by demagnetizing fields
V. V. Dmitriev+, M. S. Kutuzov*, A. A. Soldatov+×, A. N. Yudin+°
+P.L. Kapitza Institute for Physical Problems of RAS, 119334 Moscow, Russia
*Metallurg Engineering Ltd., 11415 Tallinn, Estonia
×Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
°National Research University Higher School of Economics, 101000 Moscow, Russia
Abstract
Magnetic materials generate demagnetizing field that depends on
geometry of the sample and results in a shift of magnetic resonance
frequency. This phenomenon should occur in porous nanostructures as well,
e.g., in globally anisotropic aerogels. Here we report results of nuclear
magnetic resonance experiments with liquid 3He confined in
anisotropic aerogels with different types of anisotropy (nematic and
planar aerogels). Strands of aerogels in pure 3He are covered by a few
atomic layers of paramagnetic solid 3He which magnetization follows
the Curie-Weiss law. We have found that in our samples the nuclear magnetic resonance
shift in
solid 3He is clearly seen at ultralow temperatures and depends on
value and orientation of the magnetic field. The obtained results are
well described by a model of a system of non-interacting paramagnetic
cylinders. The shift is proportional to the magnetization of solid 3He
and may complicate nuclear magnetic resonance
experiments with superfluid 3He in aerogel.