K. R. Safiullin

Size Effect in the (PrF 3 Nanoparticles- 3 He) System

Spin kinetics of adsorbed and liquid 3He in contact with crystalline nanopowders of the Van Vleck paramagnet PrF3 at a temperature of 1.5 K has been studied by nuclear magnetic resonance. The correlation between the parameters of the nuclear magnetic relaxation of 3He and the sizes of the sample particles has been found. A qualitative model of the magnetic relaxation of 3He describing the experimental results has been proposed.

Anomalous nuclear spin–lattice relaxation of 3Не in contact with ordered Al2O3 aerogel

Spin–lattice relaxation of 3Не in contact with the ordered Al2O3 fiber aerogel has been studied at the temperature of 1.6 K in fields of 0.1–0.5 T by the pulsed nuclear magnetic resonance (NMR) method. An additional mechanism of the relaxation of 3Не in aerogels is found and it is shown that this relaxation mechanism is not associated with the adsorbed layer. A hypothesis about the influence of intrinsic paramagnetic centers on the relaxation of gaseous 3Не is proposed.

Annealing of PrF3 nanoparticles by microwave irradiation

The influence of microwave irradiation on the recovery of nanocrystalline PrF3 powders has been experimentally analyzed by nuclear magnetic resonance (NMR) at T = 1.5 K. It is established that the relaxation times of 141Pr and 19F nuclei rise significantly with an increase in the hydrothermal-treatment time, whereas the 141Pr NMR spectra narrow, which indicates a decrease in the number of defects in the lattices of nanosamples.

The influence of restricted geometry of diamagnetic nanoporous media on 3He relaxation

This is an experimental study of the spin kinetics of 3He in contact with diamagnetic samples of inverse opals SiO2, and LaF3 nanopowder. It is demonstrated that the nuclear magnetic relaxation of the absorbed 3He occurs due to the modulation of dipole-dipole interaction by the quantum motion in the two-dimensional film. It is found that the relaxation of liquid 3He occurs through a spin diffusion to the absorption layer, and that the restricted geometry of diamagnetic nanoporous media has an influence on the 3He relaxation.

Comments on the cross-relaxation effect between adsorbed 3He and PrF3 nanoparticles

The spin kinetics data of 3He in contact with PrF3 and LaF3 nanosized powders are reported. All experiments have been carried out by pulse NMR methods at temperature 1.5 K. The analysis of obtained data testifies in favor of cross-relaxation presence in the nuclear spin–lattice relaxation data, which takes place between 3He and 141Pr nuclei.

Bose-Einstein condensation in antiferromagnets at low temperatures

The Bose-Einstein condensation (BEC) was predicted by Einstein in 1925 and this effect is characterized by the formation of a collective quantum state, when macroscopic number of particles is governed by a single wave function. The BEC of magnons was discovered experimentally in superfluid phase of 3He. In the present work we report our progress on the BEC of magnons investigations in solid antiferromagnets at low temperatures by magnetic resonance methods. The duration of the FID signal in two samples of easy-plane antiferromagnets CsMnF3 has been studied. Obtained data confirm the formation of magnon BEC in antiferromagnet CsMnF3.

Reply to 'Comment on 'Angstrom-scale probing of paramagnetic centers location in nanodiamonds by 3He NMR at low temperatures'' by A. Shames, V. Osipov and A. Panich, Phys. Chem. Chem. Phys., 2018, 20, DOI: 10.1039/c8cp03331e

Shames et al. made a comment on our article (DOI: 10.1039/C7CP05898E) stating that their experience in EPR studies of detonation nanodiamonds suggests the existence of two main types of paramagnetic center in detonation nanodiamonds which questions our results. In this reply we provide insights into why there is only one main type of paramagnetic centers detected in nanodiamonds used in this work, which validates the correctness of the proposed original method to determine the distances between paramagnetic centers and nanoparticle surfaces by 3He NMR.

Spin Kinetics of Liquid 3He in Contact with a DyF3 Micropowder at Ferromagnetic Ordering of Dy3+ Ions

The spin kinetics of liquid 3He in contact with a mixture of LaF3 (99.67%) and DyF3 (0.33%) micropowders at temperatures of 1.5–3 K has been studied by pulsed nuclear magnetic resonance (NMR). The DyF3 is a dipolar dielectric ferromagnet with the phase transition temperature Tc= 2.55 K, whereas the diamagnetic fluoride LaF3 is a diluting substance for the optimal observation conditions of 3Не NMR in powder pores. The magnetic phase transition in DyF3 is accompanied by a considerable change in the character of fluctuations of the magnetic moments of dysprosium ions, which affect the spin kinetics of 3Не in contact with the substrate. Significant changes in the relaxations rates of the longitudinal and transverse magnetizations of 3Не have been discovered in the region of magnetic ordering of the solid matrix. The technique of studying the static and fluctuating magnetic fields of a solid matrix at low temperatures using liquid 3He as a probe has been proposed.

Goldstone mode of a magnon Bose−Einstein condensate in MnCO 3

The low-frequency phase modulation of a radio-frequency field is used to excite a low-frequency collective mode in the Bose−Einstein condensate (BEC) of quasinuclear magnons in an antiferromagnetic material with the Suhl−Nakamura interaction. This oscillation mode is similar to the Goldstone torsional mode observed in antiferromagnetic superfluid 3He–B. The results clearly demonstrate the existence of the BEC in the systems under study.

The spin kinetics of 3He in contact with nanosized crystalline powders LaF3

The spin kinetics of 3He in contact with nanosized crystalline powders LaF3 has been studied by NMR methods at the temperature 1.5 K. The 3He longitudinal relaxation time increases proportionally to the magnitude of the external magnetic field and the transverse relaxation time does not depend on the magnetic field. Relaxation of the gaseous and liquid 3He in contact with nanosized crystalline powder LaF3 takes place by the 3He adsorbed layer. The nuclear magnetic relaxation of adsorbed 3He layer on the surface of LaF3 nanoparticles is due to the two-dimensional spin-diffusion motion.