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Register a new userNMR of 3He in contact with PrF3 nanoparticles at low temperatures
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Two nanosized PrF3 samples were synthesized using two different procedures. The X-ray and HRTEM experiments showed high crystallinity of synthesized sample. Comparison of enhanced 141Pr NMR spectra of microsized (45 $mu$m) and nanosized PrF3 powder is presented. Experimental data on spin kinetics of 3He in contact with PrF3 nanoparticles at T = 1.5 K are reported.
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The six nanosized PrF3 samples were synthesized using two different chemical reactions and different time of hydrothermal reaction. The X-ray and HRTEM experiments showed high crystallinity of synthesized samples. For all samples the particles size distribution was obtained. It was shown, that precursors of chemical reaction have influence on the shape of synthesized nanoparticles. The size of nanoparticles depended on the time of hydrothermal reaction as much as roughly 10 nm per hour.
We report on orientation of the order parameter in the 3He-A and 3He-B phases caused by aerogel anisotropy. In 3He-A we have observed relatively homogeneous NMR line with an anomalously large negative frequency shift. We can attribute this effect to an orientation of orbital momentum along the axis of density anisotropy. The similar orientation effect we have seen in 3He-B. We can measure the A-phase Leggett frequency, which shows the same energy gap suppression as in the B-phase. We observe a correlation of A - B transition temperature and NMR frequency shift.
In a highly polarized liquid (laser-polarized 3He-4He mixtures in our experiment), dipolar magnetic interactions within the liquid introduce a significant nonlinear and nonlocal contribution to the Bloch equation that leads to instabilities during NMR evolution. We have launched a study of these instabilities using spin echo techniques. At high magnetizations, a simple 180 degree rf pulse fails to refocus magnetization, so we use a standard solid-state NMR pulse sequence: the magic sandwich. We report an experimental and numerical investigation of the effect of this sequence on unstable NMR evolution. Using a series of repeated magic sandwich sequences, the transverse magnetization lifetime can be increased by up to three orders of magnitude.
119Sn nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rate (1/T1) in SnO2 nanoparticles were measured as a function of temperature and compared with those of SnO2 bulk sample. A 15% loss of 119Sn NMR signal intensity for the nano sample compared to the bulk sample was observed. This is indicative of ferromagnetism from a small fraction of the sample. Another major finding is that the recovery of the 119Sn longitudinal nuclear magnetization in the nano sample follows a stretched exponential behavior, as opposed to that in bulk which is exponential. Further, the 119Sn 1/T1 at room temperature is found to be much higher for the nano sample than for its bulk counterpart. These results indicate the presence of magnetic fluctuations in SnO2 nanoparticles in contrast to the bulk (non-nano) which is diamagnetic. These local moments could arise from surface defects in the nanoparticles.
The results of studies of supercooling upon crystallization value of Bi, Sn and Pb nanosized particles on the Al substrate and between the Al layers have been presented. It has been shown the efficiency of usage of layered film systems for investigation of the limiting supercooling in particle-matrix systems with an eutectic type of interaction between components. The obtained results have been discussed and compared with literature data. ----- Predstavleny rezultaty issledovanij pereohlazhdenij pri kristallizacii nanorazmernyh chastic Bi, Sn i Pb na Al podlozhke i mezhdu sloyami alyuminiya. Pokazana effektivnost ispolzovaniya sloistyh plenochnyh sistem dlya issledovaniya predelnogo pereohlazhdeniya v sistemah chastica-matrica s evtekticheskim tipom vzaimodejstviya mezhdu komponentami. Poluchennye rezultaty obsuzhdeny i sopostavleny s literaturnymi dannymi.
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