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The temperature dependences of the lattice parameters are investigated on the perovskite-like structures Eu1+x(Ba1-yRy)2-xCu3O7-d with Ba substitution by light rare earth, using x-ray diffraction techniques. A negative thermal expansion effect is observed and explained in detail. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The exchange coupling of magnetically ordered layers (MOLs) through a nonmagnetic metallic spacer is calculated. The induced magnetization in the spacer, taking into account the influence of an external magnetic field, is calculated, too. This calculation shows that the energy of coupling of the MOLs through the nonmagnetic metallic spacer is a long-periodic function of the spacer thickness and magnetic field, i.e., the exchange coupling between the layers varies from ferromagnetic to antiferromagnetic and vice versa depending on the spacer thickness and magnetic field. Also this calculation shows that in nonferromagnetic spacer the induced magnetization can undergo many complete rotations, depending on distance to the boundaries with the MOLs. Moreover, absolute value of the induced magnetization decays nonmonotonically with distance from the interfaces inside the spacer. It is shown that the character of the decay of the absolute value of the magnetization from the interfaces into the interior of the spacer is influenced by magnetic field. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The transformation of the magnetic absorption spectra of a narrow-band ferromagnetic conductor containing local f and quasilocal d magnetic moments under conditions of weak spin–lattice coupling and spatial randomization of the g factors of the quasilocal and local spin subsystems is investigated. It is shown that randomization of the g factors (e.g., as a result of the introduction of an impurity) leads mainly to the “opening” (i.e., to the appearance in the magnetic absorption spectrum) of acoustic and optical magnon bands formed in the system while not affecting the position and shape of the narrow magnetic resonance lines comprising the spectrum of the impurity-free crystal. The effects of spin–lattice coupling, besides the “opening” of the phonon and magnon bands, lead to a shift and a temperature smearing of the narrow resonance lines. The relative corrections to the effective magnon masses generated by the spin–lattice coupling in a 4f–5d metal amount to ∼2×10-4 for an acoustic mode and to ∼4×10-4 for an optical mode. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The equations for the nuclear magnetizations which describe the dynamics of nuclear spin-systems with strong Larmor and Rabi inhomogeneous broadenings of the NMR line under conditions of their nonequilibrium are obtained in the framework of the Mims transformation matrix method; these equations have been obtained previously by the statistical tensors method. As an example, the properties of the proton single-pulse echo and its secondary signals in a test material (silicone oil) coated on the surface of high-Tc superconducting-oxide powders and in metallic hydride are presented. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A model is proposed which describes the formation and reversible rearrangement of the equilibrium domain structure in bulk antiferromagnets with a rather strong magnetoelastic coupling. The model is based on the assumed existence of a microscopic ordering of a tensor nature—the microstress tensor that arises due to magnetoelastic coupling during the formation of the magnetic moment. It is necessary to take such a parameter into account for adequate description not only of the macroscopic internal stresses and the spontaneous strains corresponding to them but also of the microstructure of the crystal (e.g., the domain structure). The microstresses arising locally in each unit cell are equivalent, from a formal standpoint, to elastic dipoles, and they create long-range fields whose contribution to the free energy of the crystal is analogous to that of the magnetostatic energy in ferromagnets and favors a decrease in the macroscopic strain of the sample through the formation of an equilibrium domain structure. The corresponding contribution is given the name “destressing energy” by the authors. It is shown that taking this energy into account in antiferromagnetic crystals allows one not only to explain the cause of the formation of the domain structure but also to trace its dependence on the shape of the crystal and the external fields. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The vibrational spectrum of a one-dimensional disordered chain of atoms with light isotopic substitutional impurities is calculated numerically for frequencies near a local mode of an isolated impurity atom. It is shown that in the entire frequency region accessible to the calculation, the spectrum does indeed have the characteristic features of a fractal. Series of lines clustered around the lines of an isolated impurity atom or of two and three impurity atoms are examined. It is shown that in these cases a self-similar structure is preserved at arbitrary reductions of the scale both outside and inside the concentration broadening region. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The ESR spectrum of a powder sample of the metal-organic complex Cu(C10H8N2)(H2O)2SO4 is investigated in the temperature interval 2–30 K. It is found that the orbital ground level of the Cu2+ ion in this compound is the Kramers doublet |x2-y2>. The temperature dependences of the effective g-factor components and of the resonance linewidth ΔH of individual powder particles are obtained. Low-temperature broadening of the resonance line connected with short-range magnetic order in the system is observed. An estimate of the value of the exchange coupling in the magnetic system is made. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

It is shown that a strong disorder in the distribution of exchange couplings between magnetic impurities and hosts in quantum spin chains and non-Fermi-liquid rare-earth and actinide compounds can be the cause of magnetic orderings in these systems at low temperatures. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The ESR spectrum of a powder sample of the metal-organic complex Cu(C10H8N2)(H2O)2SO4 is investigated in the temperature interval 2–30 K. It is found that the orbital ground level of the Cu2+ ion in this compound is the Kramers doublet |x2-y2>. The temperature dependences of the effective g-factor components and of the resonance linewidth ΔH of individual powder particles are obtained. Low-temperature broadening of the resonance line connected with short-range magnetic order in the system is observed. An estimate of the value of the exchange coupling in the magnetic system is made. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]