Nuclear magnetic resonance study of langatate

A langatate crystal was studied using the nuclear magnetic resonance method. The temperature dependence of the spin-lattice relaxation rate of ⁷¹Ga nuclei was measured in a single-crystal sample in the range 294–500 K. It was shown that the relaxation rate depends linearly on the square of the temperature. The shape of the powder spectrum obtained under static conditions was found to correspond to large values of the quadrupole coupling constant of gallium nuclei. The measurements of the powder spectra obtained upon magic-angle spinning made it possible to estimate the quadrupole coupling constant for gallium in the tetrahedral and octahedral oxygen coordinations.     

Fluorine mobility in an aluminum-doped CeF<Subscript>3</Subscript> crystal: NMR and conductivity studies

Electrical conductivity and NMR measurements were carried out for an aluminum-doped CeF₃ crystal to study the influence of substitutional impurities on the superionic fluorine mobility. Activation enthalpy was found to remain constant from low temperatures to about 325 K and to increase as compared to that of a pure CeF₃ crystal. Above about 325 K, a trend towards gradual conductivity saturation was observed. This change was ascribed to a superionic phase transition not accompanied by structural transformations. NMR also revealed some alterations in the local fluorine dynamics as compared to that reported for a pure CeF₃ crystal. According to NMR measurements, the superionic phase transition near 325 K results in acceleration of the exchange between rigid or slow fluorine in the F₁, F₂, and F₃ sublattices, while highly mobile F₁ fluorine ions move independently at least until 400 K.     

Nuclear magnetic resonance investigation of metallic sodium nanoparticles in porous glass

Sodium nanoparticles embedded in porous glass have been studied by NMR. The measurements have been carried out on pulse spectrometers in magnetic fields of 9.4 and 17.6 T in a wide temperature range. Changes in the magnitude and temperature dependence of the ²³Na Knight shift with respect to those in bulk sodium have been discovered. An additional component of the NMR line shifted to high frequencies has been observed in the temperature range from 240 to 100 K. Investigation of the specific heat has revealed a considerable decrease in the melting and crystallization temperatures of sodium under nanoconfinement, which were not accompanied by abrupt changes in the Knight shift.     

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.     

Magnetic properties of a cermet on the base of Al2O3

The zero-field-cooled and field-cooled magnetizations, magnetization versus field, and remanent magnetization were measured for a cermet on the base of Al₂O₃ using a SQUID magnetometer in the temperature range of 2–360 K. It was shown that magnetic properties of the cermet are determined by independent ferromagnetic, paramagnetic and spin-glass contributions. The spin-glass behavior was studied.     

Evolution of NaNO<Subscript>2</Subscript> in porous matrices

NMR and dielectric studies of NaNO₂ loaded into an SBA-15 mesoporous matrix are reported. The spin-lattice relaxation rate and the ²³Na NMR line shift, as well as the permittivity, were measured within a broad temperature interval including the ferroelectric phase transition in NaNO₂. The phase transition temperature of sodium nitrite in as-prepared samples was shown to differ substantially from that characteristic of a bulk crystal. The permittivity grows strongly in the vicinity of the phase transition. Heating a sample causes the properties of NaNO₂ embedded in pores to gradually approach those of bulk crystals.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.     

Magnetic Properties of Iron-Doped Bi2Se3, a Topological Insulator

Physics of the Solid State - We study the dc magnetization of a Bi1.94Fe0.06Se3 single crystal in the temperature range of 1.9&nbsp;to 400 K in applied magnetic fields up to 70 kOe for two...     

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...     

Kinetic Characteristics of Phonons and the Structural Heterogeneities of the Monoaluminate Y 1 – x Er x AlO 3 Solid Solutions

The low-temperature specific heat, the transport characteristics of phonons at the helium temperatures, and the nanostructural heterogeneities in the erbium monoaluminate YAlO3:Er solid solution single crystals synthesized by directional solidification are studied.