M. S. Tagirov

Spin Kinetics of 3He in Contact with Synthesized PrF3 Nanoparticles

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

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

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

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.

Experimental proof of the existence of water clusters in fullerene-like PrF3 nanoparticles

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.

Nuclear pseudoquadrupole resonance of 141Pr in Van Vleck paramagnet PrF3

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.

Observation of magnetic coupling between the nuclei of liquid 3He and the 141Pr nuclei of PrF3 crystalline powder

Synthesized fullerene-like nanoparticles of the Van Vleck paramagnet PrF3 have been studied by nuclear magnetic resonance cryoporometry. Water clusters have been discovered in the internal cavities of the nanoparticles. The analysis of the experimental data indicates that the cluster radius is 1–2.3 nm. The obtained data agree well with the high-resolution transmission electron microscopy data.

169Tm NMR study of the high-Tc superconductor TmBa2Cu3O6.92

Nuclear pseudoquadrupole resonance of 141Pr in Van Vleck paramagnet PrF3 has been observed in singlecrystal and micro- and nanopowder samples at a temperature of 4.2 K. The spectra of nuclear pseudoquadrupole resonance of 141Pr, as well as the spin-spin and spin-lattice relaxation parameters, have been obtained. The parameters of the nuclear spin Hamiltonian have been determined. It has been found that the parameters of the crystal electric field in nanocrystals differ strongly from those in microcrystals.

NMR of Liquid 3He in Pores of a Clay Sample

The resonance magnetic coupling between the nuclei of liquid 3He and the 141Pr nuclei of a fine-dispersed powder of PrF3 Van Vleck paramagnet with the grain size below 45 μm has been discovered at a temperature of 1.5 K with the use of a pulsed NMR technique. The magnetic specific heat of the corresponding spin systems is estimated theoretically.

Magnetism and structural phase transitions in LiTmF4 powders

The ground state of Tm3+ ion (4t2,3H6) in a crystal electric field (CEF) of TmBaCuO is a singlet, separated from the lowest excited states by an energy gap of 100÷130 cm−1. The pulsed NMR of169Tm nuclei (spinI=1/2) in a magnetically-oriented TmBa2Cu3O6.92 power is studied at temperatures 1.5÷4.2 K. Two sorts of Tm nuclei are observed: rapidly relaxing Tm1 (≥80% of total amount, having relaxation timesT1(1)≈35 ms,T2(1)=80÷250 μs) and slowly relaxing Tm2 nuclei (≦20%,T1(2)=300÷1000 μs). The169Tm NMR spectra are described by the spin-Hamiltonian ℋ1 = −ℏΣγiHiIi (i = x,y,z), where |γx(1)/2π| = 5.3(1), |γy(1)/2π| = 6.6(1), |γx(2)/2π| = |γy(2)/2π| = 5.1(1), |γz(1)/2π| = |γz(2)/2π| = 2.3(1) kHz/Oe, and axesx, y, z coincide with the crystal axesa, b, c. The Tm1 and Tm2 nuclei are identified as those belonging to orthorhombic (CEF of D2h symmetry) and tetragonal (D4h) phases of the TmBaCuO compound, respectively. Two-exponential and nearly temperature-independent nuclear relaxation is observed at temperatures 1.5÷4.2 K. The smallestT2(1)-values (≈80 μs) found for the orthorhombic (superconducting) phase in an external field H perpendicular to the crystalc-axis agree fairly well with those one could expect due to the dipole-dipole interaction of thulium nuclei. However, the slowing down of this rapid relaxation of the nuclear transverse magnetization in a field H‖c as well as the origin of unusually largeT2(2)-values remain unclear.

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

In the present work a new method for studying porous media by nuclear magnetic resonance (NMR) of liquid 3 Не has been proposed. This method has been demonstrated in an example of a clay mineral sample. For the first time the integral porosity of clay sample has been measured. For investigated samples the value of integral porosity is in the range of 10-30 %. Inverse Laplace transform of 3 He longitudinal magnetization recovery curve has been carried out, thus distribution of relaxation times T1 has been obtained.