A. L. Buzlukov

Features of the magnetic state of ƒ electrons in the stabilized δ phase of the Pu0.95Ga0.05 alloy

For the Pu0.95Ga0.05 alloy belonging to the stabilized δ phase of the Pu-Ga system, the 69Ga NMR spectra are measured in the temperature interval 10–650 K and the static magnetic susceptibility χ is measured in the interval T = 20–350 K. In the region T > T* = 235 K, the temperature-dependent magnetic part of the shift K(T) of the Ga NMR line reproduces the χ(T) dependence and follows the Curie-Weiss law K(T) ∼ (T + Θ)−1 with Θ = 280(40) K, which is typical of incoherent spin fluctuations of localized ƒ electrons in concentrated nonmagnetic Kondo systems. The estimate of the effective magnetic moment μeff, 5ƒ(ge = 2) = 0.15(5)μB per Pu atom testifies to a strong suppression of the spin magnetism in the alloy, where the configuration of the ƒ shell of a Pu ion is close to atomic-like ƒ6. The difference between the K(T) and χ(T) dependences observed for the alloy in the temperature range T < T* is analyzed in terms of the two-fluid description of Kondo lattices developed by Pines et al. [15, 16] in application to the coherent state of a heavy-fermion liquid. Possible causes for the anomalous increase in long-wave contributions in the spatial dispersion of the localized spin susceptibility component of ƒ electrons χƒƒ at temperatures below 50 K are discussed.

Magnetic structure of the low-dimensional magnet NaCu2O2: 63,65Cu and 23Na NMR studies

The magnetic structure of a quasi-one-dimensional frustrated NaCu2O2 magnet single crystal is studied by NMR. The spatial orientation of the planar spin spirals in the copper-oxygen Cu2+-O chains is determined, and its evolution as a function of the applied magnetic field direction is analyzed.

Helical magnetic structure in a quasi-one-dimensional LiCu2O2 multiferroic crystal according to 63,65Cu NMR studies

The NMR spectra of 63Cu and 65Cu natural copper isotopes in a LiCu2O2 multiferroic single crystal compound have been measured above and below the temperature of magnetic phase transition (Tc = 23 K) in zero magnetic field and in applied magnetic field H0 = 94 kOe parallel to the c axis of the crystal. In LiCu2O2 below Tc, a complicated helical magnetic structure with the magnetic moment of copper ions Cu2+ varying along the chain according to the harmonic law with the wave vector being incommensurate to the crystal lattice constants has been revealed. The experimental results have been successfully interpreted using the model based on the planar helical magnetic structure. It has been found that the plane of rotation for Cu2+ magnetic moments in LiCu2O2 does not coincide at H0 = 0 with the ab plane. The high magnetic field (H0 = 94 kOe) applied along the c axis of the single crystal does not affect the spatial orientation of the plane of rotation.

Inhomogeneous state of the electron system in BaPb1 − xSbxO3 superconducting perovskites: The 207Pb NMR study

Comprehensive measurements of the 207Pb NMR spectra, Knight shifts 207Ks, spin-lattice relaxation rate 207T1−1, and the Pb spin echo decay 207E(2t) in BaPb1 − xSbxO3 superconducting oxides (x ≤ 0.33) have been performed. A considerable increase in the shift distribution width when Sb is substituted for Pb indicates the formation of the inhomogeneous state of the electron system in the oxide conduction band. The shift magnitude proportional to the density of states near the Fermi energy, 207Ks ∝ N(EF), reaches its maximum in the compounds with x = 0.18–0.25 with the maximum temperatures Tc of the superconducting transition. In the BaPb1 − xSbxO3 compounds, the Korringa relation is met, indicating that all of the samples are in the metal phase. The data on the Pb spin echo decay and the relevant estimates of the indirect coupling constants of the nuclei of the nearest neighbor Pb atoms clearly demonstrate the development of the electron system state in the oxide metal phase, which is microscopically inhomogeneous over the crystal.