On the 240 K anomaly in the magnetic properties of LiNiO2

In this work, results of X-band ESR spectroscopy, ac-magnetic susceptibility and X-ray powder diffraction measurements on Li_1-xNi _1+x O₂ (x = 0.02 and x = 0.07) are presented and discussed. While the susceptibility of the compound with x = 0.02 is shown to follow a Curie-Weiss law, with a Weiss temperature of the order of 30 K, the compound with x = 0.07 is found to order ferromagnetically below K. However, an additional anomaly is observed in the magnetic properties of this latter compound at around 240 K. We attribute this anomaly to the presence of macroscopic Ni-rich regions which order ferrimagnetically below this temperature. This phenomenon is different from the bulk ferromagnetism that occurs at much lower temperatures, and allows us to discard earlier suggestions proposed in the literature in which the 240 K anomaly has been considered as denoting an intrinsic phenomenon. Received 14 May 1999 and Received in final form 5 August 1999     

Magnetic properties of the S = 1/2 one-dimensional antiferromagnet MgVO

The magnetic susceptibility and the electron spin resonance in the X-band of the transition metal oxide compound MgVO₃ are reported. We show that this compound, made of weakly coupled infinite chains of VO₅ pyramids, behaves as a S =1/2 one-dimensional Heisenberg antiferromagnet. From the ESR and magnetic experiments we deduce the Néel temperature K, the in-chain coupling constant K and the g-factor values g x = g z =1.972(2), g y =1.946(1) for V⁴⁺ ions in MgVO₃. Received 14 July 1999     

An analytic method in general relativity

An analytic method, which Wu called the “Bochner technique,” has been used for fifty years to describe global Riemannian and Kähler geometries. We use this method to describe conformally Killing vector fields and harmonic timelike vector fields on a Lorentzian manifold and to study hydrodynamic models of the Universe, the existence of closed spacelike sections, and the possibility of fibering Lorentzian manifolds.     

Focusing Waveguide Structure for High-Gradient Electron Acceleration by Picosecond Terahertz Pulses

Radiophysics and Quantum Electronics - We propose an ultra-wideband metal–dielectric structure for high-gradient acceleration of electrons by the field of an ultrashort terahertz pulse. The...     

Application of the EBSD Method to Study the Fracture Mechanisms of Reactor Pressure Vessels Steels under Operational Factors

Crystallography Reports - The mechanisms of degradation of the structure and properties of steels of pressure vessels of pressurized water reactors (PWRs) have been analyzed using еlectron...     

Effect of a Low-Frequency Magnetic Field on the Release of Heat by Magnetic Nanoparticles of Different Shapes

Russian Journal of Physical Chemistry A - Cubic nanoparticles of magnetite are synthesized and a comparative analysis is performed of the release of heat by needle-shaped and spherical...     

Spatial Vector–Scalar Structure of Low-Frequency Fields of Multipole Sources in Interference Maxima Zones

Acoustical Physics - For low-frequency multipole sources of various orders in a Pekeris waveguide, we have obtained and studied the dependences that determine the change in the structure and...     

On optimal Banach spaces containing a weight cone of monotone or quasiconcave functions

Optimal (minimal) Banach spaces containing given cones of monotone or quasiconcave functions on the semiaxis from weighted Lebesgue spaces are described. Exact formulas for the norm of the optimal space are presented. All cases of the summation parameter are studied.     

Determination of Physicochemical Forms of Iodine-131 in Ejector Gases during Operation of the Industrial Reactor Facility at FSUE Mayak Production Association

Physics of Atomic Nuclei - On the basis of the recommendations of the IAEA and the requirements of domestic regulatory documents, a study is conducted to determine the activity of aerosol and...     

System of Solid Targets for the Production of a Wide Range of Radionuclides

Physics of Particles and Nuclei Letters - CC series cyclotrons manufactured by the JSC Efremov Research Institute of Electrophysical Apparatus (NIIEFA) are intended primarily for the production of...