A Possible Liquid–Liquid Transition in a Ga–In Melt Introduced into an Opal Matrix

Physics of the Solid State - The temperature evolution of the Ga94In6 liquid alloy introduced into an opal matrix has been studied by the NMR method in the temperature range 300–155 K. The...     

Structural Evolution of Diisopropylammonium Chloride (DIPAC) Molecular Ferroelectric

Physics of the Solid State - Room-temperature changes in the structure of a new diisopropylammonium chloride (C6H16ClN, DIPAC) molecular ferroelectric have been investigated by high-resolution...     

Atomic mobility in a ternary liquid Ga–In–Sn alloy of the eutectic composition

The nuclear spin–lattice relaxation and Knight shift of ⁷¹Ga, ⁶⁹Ga, and ¹¹⁵In nuclei in a ternary liquid gallium–indium–tin alloy of the eutectic composition, which was introduced into pores of an opal matrix and porous glasses with pore sizes of 18 and 7 nm, have been investigated and compared with those for the bulk melt. It has been found that longitudinal relaxation is accelerated and the Knight shift is decreased, depending on the size of pores. The correlation time of the atomic motion has been calculated for the nanostructured melt in porous matrices. It has been shown that the atomic mobility in the melt decreases with decreasing size of pores in the glasses.

     

Slowdown of atomic diffusion in liquid gallium–indium alloy under different nanoconfinements

NMR studies were carried out on three isotopes, ⁷¹Ga, ⁶⁹Ga, and ¹¹⁵In, in liquid gallium-indium (Ga–In) alloy embedded into porous glasses with 200 and 5 nm pore sizes at two magnetic fields, 9.4 and 17.6 T. Spin-lattice relaxation and the Knight shift were found to depend on pore size. For porous glass with 5 nm pores the relaxation rate was field-dependent which evidenced that the extreme narrowing limit was no longer valid. Magnetization recovery data were used to evaluate the correlation times of atomic mobility and the quadrupole constants under nanoconfinement.     

NMR study of topological insulator Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> in a wide temperature range

NMR studies of ¹²⁵Te in the topological insulator bismuth telluride Bi₂Te₃ in a wide temperature range from room temperature to 12.5 K are performed. The pulsed NMR spectrometer Bruker Avance 400 is applied. The NMR spectra are obtained for the powder from Bi2Te3 single crystal and monocrystalline plates with the orientations c || B and c ⊥ B. At room temperature, the spectra consist of two lines related to two nonequivalent positions of tellurium nuclei Te1 and Te2. The parameters of the NMR frequency shift tensor are found from the powder spectrum. The temperature dependences of the spectra for the powder and plates with the orientation c ⊥ B agree with each other. The line shift with decreasing temperature is explained by the reduction of the Knight shift. The thermal activation energy of charge carriers is estimated. The spectra for the plates with the orientation c || B demonstrate peculiar behavior below 91 K. The spin-lattice relaxation time for the powder and monocrystalline plates with both orientations at room temperature is measured.     

Nuclear magnetic resonance study of potassium dihydrophosphate

A powder sample of potassium dihydrophosphate KH₂PO₄ has been studied by the ³¹P NMR method in a wide temperature range covering the ferroelectric phase transition. Changes in the position and shape of the resonance line at the transition to the ferroelectric phase have been revealed. The parameters of the chemical shift tensor of ³¹P (isotropic shift, anisotropy, and asymmetry) in the ferroelectric phase have been calculated from the experimental data. A sharp increase in the anisotropy of the tensor at the phase transition has been demonstrated. Dielectric measurements have also been carried out to verify the transition temperature.     

NMR Studies of a Nanocomposite Based on Molecular Ferroelectric Diisopropylammonium Bromide

Applied Magnetic Resonance - The properties of the molecular ferroelectric diisopropylammonium bromide (C6H16BrN, DIPAB) particles embedded into a nanoporous opal matrix were studied by...     

Diffusion slowdown in the nanostructured liquid Ga‐Sn alloy

The diffusion of gallium in liquid Ga‐Sn alloy embedded into different porous silica matrices was studied by NMR. Spin relaxation was measured for two gallium isotopes, ⁷¹Ga and ⁶⁹Ga, at two magnetic fields. Pronounced rise of quadrupole contribution to relaxation was observed for the nanostructured alloy which increased with decreasing the pore size. The correlation time of atomic mobility was evaluated and found to be much larger than in the relevant bulk melt which evidenced a pronounced diffusion slowdown in the Ga‐Sn alloy under nanoconfinement. It is shown that the diffusion was slower by a factor of 30 for the alloy within 7 nm pores. The spectral densities of electric field gradients at zero frequency were found to double for the finest pores. The Knight shift was found to decrease but slightly for the nanostructured alloy.     

Dynamical shift of NMR lines in nanostructured Ga–In–Sn melt

Physics of the Solid State - NMR spectrum and recovery of longitudinal nuclear magnetization after inverting pulses were measured for isotopes 69Ga and 71Ga in a liquid eutectic alloy...     

Influence of size effects on the Knight shift of NMR lines in the gallium-indium alloy

A study is reported of the Knight shift of ⁷¹Ga, ⁶⁹Ga, and ¹¹⁵In NMR lines in a liquid gallium-indium alloy with a composition of 90 at % Ga and 10 at % In, introduced into porous glasses with pore sizes of 5 and 200 nm, relative to the corresponding shifts in the bulk alloy. The measurements have been performed at room temperature. The study has revealed a size-dependent decrease in the Knight shift. A sample with a 5-nm pore size has demonstrated a noticeable difference in the magnitudes of the Knight shift of both gallium isotopes measured in magnetic fields of 9.4 and 17.6 T, which implies a dependence of the electronic susceptibility of the melt on the magnetic field under the nanoconfinement conditions.