Spin susceptibility and low-frequency dynamics of uranium 5f electrons have been investigated by nuclear magnetic resonance (NMR) on the N-14 nuclei in paramagnetic and magnetically ordered phases for single crystalline and polycrystalline samples of uranium mononitride (UN). NMR spectra, shifts of the N-14 NMR lines, and the spin-lattice relaxation times T-1 have been obtained in the temperature range T = 10-760 K in magnetic field B = 92.8 kOe. It is shown that in the UN paramagnetic phase, temperature dependence of the N-14 NMR line shift is proportional to the spin susceptibility of the uranium 5f electrons. Joint analysis of NMR and magnetic susceptibility data allows us to determine temperature dependence of spin fluctuation energy F (T) of the uranium 5f electrons and to demonstrate that its temperature variation is close to Gamma (T ) alpha T-0.5 dependence which is characteristic of the concentrated Kondo systems above the coherent state formation temperature. In the magnetically ordered UN phase the N-14 NMR spectra consist of several lines that can be explained in terms of the model of type I antiferromagnetic order corresponding to 1k structure in the presence of magnetic domains.

In the paramagnetic phase of cubic antiferromagnet SrMnO2.997 (T-N = 236 K), the spin susceptibility of the localized Mn(t(2g)) electrons exhibits a gapped behavior with d chi(s) (T) >= 0, suggesting the existence of a low-dimensional short-range magnetic order above T-N. The low-frequency fluctuations of the spin correlations of neighboring Mn4+ ions were probed by measuring the spin-lattice relaxation rate T-1(-1) and the echo-decay rate T-2(-1) of O-17 and Sr-87 nuclei up to 420 K. O-17 being involved in an Mn-O-Mn bond, the echo-decay rate T-17(2)-1 probes the fluctuations of the two neighboring S(t(2g)) spins at low frequency, omega <= 10(3) s(-1). It is shown that there exist local changes of the double-exchange interaction, which favor FM correlated pairs of neighboring S(t(2g)) spins in the Mn-O-17-Mn bond. The unusual thermal behavior of T-17(2)-1 (T) indicates low-frequency fluctuations of the short-range magnetic order which may include the change of AF <-> FM spin alignment of neighboring magnetic ions. For Sr-87 nuclei, which probe the spin configuration of eight neighboring Mn ions in the cubic unit cell, T-87(2)-1 has no such anomaly, implying that FM order should be excluded within the cubic unit cell. With both NMR probes, it is deduced that the only magnetic orders which may exist in the cubic unit cells are the following: AF-G [q = pi/a(1, 1, 1)], AF-C [q = pi/a(1, 1, 0)], and AF-A [q = pi/a(0, 0, 1)] so that the slow fluctuating short-range magnetic order is built from these three AF ordered unit cells. Furthermore, we deduce from T-17(1)-1 results that the fluctuating short-range magnetic order, i.e., corresponding to large q, has a high thermal stability in the PM phase of SrMnO2.997.

The inhomogeneous magnetic state arising from isothermal aging of the rapidly quenched U–6Nb alloy (6.3 wt % or 14 at % niobium) was studied for the first time using nuclear magnetic resonance of the 93Nb nucleus. In the process of phase transformation during isothermal annealing at Тan = 500°C, the fraction of niobium atoms in the bulk of the alloy increases in regions with a magnetic susceptibility corresponding to the alloys U1–хNbх (х > 0.14). It is shown that the process of isothermal transformation, accompanied by the formation of niobium-enriched structural precipitates, is fully completed after 60 hours.

The spin density distribution of itinerant electrons, n eg , and their effect on pairwise correlations of localized spins S ( t 2 g ) of Mn 4+ ions in cubic Sr 1 − x La x MnO 3 antiferromagnet ( x = 0.02, T N = 230 K, G type magnetic structure) is studied experimentally by nuclear magnetic resonance on 17 O nuclei. The regions with n eg > x , in which the local spin susceptibility of pairs of Mn atoms follows the dependence χ ∼ ( T − Θ) −1 with Θ = 20(5) K, indicating the growth of ferromagnetic spin correlations of neighboring magnetic ions in these domains, are found in the paramagnetic phase. The fraction of Mn-O-Mn bonds ( n eg > x ) increases with the decrease in the temperature. The interpenetrating meshes of Mn-O-Mn bonds with different densities of itinerant e g electrons form an antiferromagnetic metal phase below T N . The role of weak localization effects is discussed as the main origin of the magnetic inhomogeneity of the antiferromagnetic metal phase in Sr 0.98 La 0.02 MnO 3 .

The results of the study of the paramagnetic region of uranium mononitride by the method of nuclear magnetic resonance (NMR)of 14N nuclei are presented.The 14N NMR spectra, the Knight shifts K, the spin-lattice relaxation times T1 have been obtained within the temperature range T = 60 – 375 K and at magnetic fields 92.8 kOe and 117.5 kOe. The temperature dependence of the Knight shift of the 14N line is proportional to the spin susceptibility χ of 5f-electrons of uranium. The ratio of the experimentally determined value TT1K2 to the theoretically calculated value of the Korringa contribution is 21.5 (at T = 295 K), which is significantly more than for common metals. This suggests that nuclear relaxation is based on the same mechanism as the Knight shift, namely, the indirect connection between the 14N nuclei and the localized magnetic moments of uranium through conduction electrons. The experimental results on the T-dependence of the spin-lattice relaxation rate of 14N also do not contradict the assumption that uranium mononitride is a concentrated Kondo system.

The results of NMR studies of the magnetic structures of LiCu2O2 and NaCu2O2 single crystals are summarized. The obtained data are discussed in the context of topical issues of the type of magnetic ordering in these compounds and the origin of ferroelectricity of LiCu2O2.

The spin susceptibility of a polycrystalline sample of uranium mononitride UN is studied by measuring the 14N NMR line shift, spin–lattice relaxation rates of the nuclear spin, and static magnetic susceptibility in the temperature region of 1.5TN < T < 7TN A joint analysis of the results obtained has revealed the temperature dependence of the characteristic energy of spin fluctuations of the uranium 5f electrons: Γnmr(T) ∝ T0.54(4) close to the dependence Γ(T) ∝ T0.5 characteristic of concentrated Kondo systems above the coherent state formation temperature.

A comprehensive NMR study of the magnetic properties of single crystal LiCu 2 O 2 (LCO) and NaCu 2 O 2 (NCO) is carried out in the paramagnetic region of the compounds for various orientations of single crystals in an external magnetic field. The values of the electric-field gradient (EFG) tensor, as well as the dipole and transferred hyperfine magnetic fields for 63,65 Cu, 7 Li, and 23 Na nuclei are determined. The results are compared with the data obtained in previous NMR studies of the magnetically ordered state of LCO/NCO cuprates.

Results of studying the paramagnetic and ordered phases of a CuCrO 2 single crystal using nuclear magnetic and nuclear quadrupole resonances on 63,65 Cu nuclei are presented. The measurements have been carried out in wide ranges of temperature ( T = 4.2–300 K) and magnetic-field strength ( Н = 0–94 kOe), with the magnetic fields being directed along a and c axes of the crystal. The components of the electric-field gradient tensor and the magnetic-shift tensor ( K a,c ) have been determined. The temperature dependences K a ( H || a ) and K c ( H || c ) for the paramagnetic phase are described by the Curie–Weiss law and reproduce the behavior of the magnetic susceptibility (χ a,c ). The hyperfine field on a copper nucleus has been determined, which is equal to h hf a,c = 33 kOe/μB. Below the temperature Т N = 23.6 K, nuclear magnetic resonance and nuclear quadrupole resonance spectra for 63,65 Cu nuclei have been recorded typical of helical magnetic structures, which are incommensurable with the lattice period.

The spin density of doped electrons was investigated by Sr-87 NMR in the paramagnetic (PM) and antiferromagnetic (AF) G-type phases of electron-doped Sr1-xLaxMnO3 (x = 0.00, 0.02, 0.04; T-N = 236-200 K) ceramics with the cubic structure. It is shown that the Sr-87 NMR shift is proportional to the local density of the itinerant doped electrons surrounding the Sr sites; these electrons have mainly the e(g) character. In the PM phase, all the doped electrons are itinerant; however, they are inhomogeneously distributed in the La-containing oxides, creating electron-doped regions (EDRs) with a number of eg electrons perMn larger than in the rest of the oxide. At room temperature, the network of the overlapping EDRs does not cover all Sr sites. Nevertheless, the number of the Sr sites inside an EDR exceeds the site percolation threshold even for x = 0.02, so that the eg electrons can move on large distances. In the AF phase, below 80 K the EDRs cover the entire crystal. In this T range the doped electrons separate into two species: some of them slow down their motion and form below 50 K static FM domains, which are considered as bound magnetic polarons (MPs) of small size with the effective moment p(eff) = 23(10) mu(B) and a MP formation energy similar to 40 meV. The second species concerns the electrons which remain itinerant at low temperature participating in the fast hopping in the AF G-type ordered lattice of the Mn4+ ions. Nevertheless, their motion is slower than what is expected in an AF metal phase without cation disorder; this is probably due to the imperfect shielding of the (La3+/Sr2+) charge disorder.

The spin susceptibility of the localized Mn(t(2g)) electrons, chi(s), and the spatially distributed spin density of the doped electrons were investigated by O-17 nuclear magnetic resonance (NMR) in the paramagnetic (PM) and antiferromagnetic (AF) phases of electron-doped SrMnO3-x ceramics with the cubic structure. Three lightly doped samples (2x < 0.015) were studied with T-N = 220 K-240 K. In the PM state chi(s) increases gradually from T-N and reaches a broad maximum above similar to 1.5T(N). The gapped behavior of chi(s) indicates a low-dimensional short-range spin order persisting above T-N. These short-range one-dimensional correlations are consistent with O-17 NMR results obtained at room temperature, which show that Mn magnetic moments are aligned along the edges of the cubic unit cell. Above 350 K all doped electrons are fast-moving e(g) electrons. They provide the uniform polarization of the localized spins which increases chi(s) and the increasing doping shifts the oxygen-deficient SrMnO3-x oxide towards a ferromagnetic (FM) metallic state. At lower T the doped electrons are heterogeneously distributed in the oxide: The fraction of the fast-moving electrons diminishes and vanishes below 100 K, while the remaining doped electrons slow down their hopping and each of them creates a FM domain. These FM domains which are detected below 10 K by Mn-55 NMR can be considered as small-size magnetic polarons. Their T-activated hopping in the G-type AF lattice was probed by O-17 spin-echo experiments. The energy barrier of hopping shows a trend to grow with increasing doping, indicating that the de Gennes metallic ground state cannot be achieved in oxygen-deficient SrMnO3-x oxides, probably due to detrimental oxygen vacancy defects.

The 1H nuclear magnetic resonance measurements were carried out to study proton dynamics features in the hydrated scandium-doped barium zirconate, BaZr1 − x Sc x O3 − x/2(OH) y , with x = 0.2 and 0.4 in the temperature range 300–600 K. The obtained data evidence a fast proton motion in both samples, which is characterized by the jump frequency of about 108 s−1 at 450 K. However, the microscopic nature of hydrogen diffusion in these two samples is quite different. For the sample with x = 0.2, hydrogen motion mechanisms are defined by a rapid chemical exchange between Sc–OH–Zr and Zr–OH–Zr positions. The estimated value of activation energy for hydrogen diffusion of about 0.5 eV is determined by the energy barrier produced by Sc3+ ion. The increase of Sc concentration to x = 0.4 leads to the drastic changes of sample properties. Experimental results allow to assume the formation of nanoscaled Sc-rich domains and the decomposition of hydrogen sublattice with formation of two proton subsystems: the protons in Zr–OH–Zr coordinations and those concentrated in Sc–OH–Sc environments. The proton motion in both these subsystems is rather fast, but the chemical exchange between them is highly suppressed. Hydrogen motion inside Sc-rich environments has most likely localized nature. Our estimates yield the energy values of about 0.25 and 0.55 eV for hydrogen motion in “free lattice” and in Sc-rich clusters, respectively. The Sc-rich domains can retain hydrogen up to 600 K.

This paper presents the results of lithium dynamics studies of monoclinic beta-Li2HfO3. The Li-6 MAS and Li-7 static NMR experiments and ab initio calculations have been performed to clarify the features of lithium motion in this layered Li-conducting oxide. It was revealed that two types of lithium motion with significantly different characteristic jump frequencies coexist at 425-900 K. One of the processes, responsible for the long-range lithium diffusion, is characterized by an activation energy of E-a = 1.00 +/- 0.05 eV and an ion jump frequency of tau(-1)(d) similar to 10(4) s(-1), at T similar to 750 K. The long-range lithium diffusion represents the successive ion jumps between the non-equivalent octahedral sites in Li/Hf and Li layers, occurring through the distinct type of tetrahedral interstitials (meanwhile, two other types of tetrahedra are less involved in motion). Another type of ion dynamics is the much more rapid localized motion of Li ions with E-a similar to 0.6 eV and tau(-1)(d) similar to 10(4) s(-1) already at T similar to 400 K. The mechanisms of lithium motion in Li2HfO3 are closely related to the features of the local crystal structure and to the presence of substitution point defects Hf -> Li.