V. V. Kuzmin

Discovery of the classical Bose-Einstein condensation of magnons in solid antiferromagnets

Results of experiments in which the Bose-Einstein condensate of magnons is created in the CsMnF3 easy-plane antiferromagnet in a system with coupled nuclear-electron precession with dynamical frequency shift are presented. This condensate is similar to the Bose-Einstein condensate of magnons in superfluid 3He-A in aerogel.

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.

Low temperature adsorption of 3He on silica aerogel surface and its influence on 3He spin kinetics

Significant influence of the aerogel surface heterogeneity on the processes of 3He nuclear magnetic relaxation at temperatures 1.5 − 4.2 K is discovered. This influence appears, for instance, in differences of the 3He T1 relaxation times for small portion of 3He, adsorbed at different temperatures. Binding energy data of 3He and distributions of this energy in two types of aerogel were obtained experimentally. Adsorbed 3He molecules with binding energies 60 – 250 K play supreme role in processes of nuclear magnetic relaxation of gaseous and liquid 3He in aerogel.

On the thermodynamic equilibrium in the 3He-aerogel system at low temperatures

A new method for studying the processes of the establishment of the thermodynamic equilibrium in the adsorbed 3He layers in highly porous media has been proposed. Using this method, the thermalization of adsorbed 3He on silica aerogel at a temperature of 1.5 K has been studied. The process of the establishment of the thermodynamic equilibrium has been controlled by measuring the pressure in an experimental cell, the amplitude of the NMR signal, and the nuclear spin-spin and spin-lattice relaxation times of adsorbed 3He. It has been shown that the establishment of the thermodynamic equilibrium in the adsorbed 3He-aerogel system is characterized by a time of 26 min.

Atomic type magnon Bose-Einstein condensation in antiferromagnet.

The Spin Supercurrent and Bose-Einstein condensation of magnons, similar to an atomic BEC, was observed in 1984 in superfluid 3He-B The same phenomena should exist in solid magnetic systems. We describe here the first observation of magnon BEC in solid easy plain antiferromagnet CsMnF3. We have observed magnon BEC on a mode of coupled Nuclear-Electron precession. The dynamical properties of this mode have many similarities with NMR of superfluid 3He-A The frequency changes with deflection of nuclear magnetization. Furthermore, the involvement of electron ordered subsystem gives the magnon-magnon interaction, spin waves and spin supercurrent, while the nuclear subsystem gives the relatively long time of relaxation.

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.