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Single-particle excitations in quasi-one dimensional ferromagnetic spin chains located in nonuniform magnetic fields with large gradients are examined. Spin waves are dynamically localized in a magnetic field with a constant gradient and a system of local levels with equidistant energies develops with a form similar to the Wannier-Zeeman “ladder.” This effect is similar to Bloch oscillations of an electron in a weak electric field. In a semi-infinite chain the spectrum of spin excitations is bounded below; with increasing energy a gradual transition from spin waves in a uniform magnetic field to states with Bloch-like oscillations occurs. An infinite spin chain in a magnetic field that is constant for x 0 is considered. Under these conditions a system of local Wannier-Zeeman states develops above the spin wave zone; their spectrum becomes equidistant at high energies. Possibilities for the experimental observation of Bloch oscillations of spin waves are discussed.

We discuss the dynamics of a magnetic soliton in a one-dimensional ferromagnet placed in a weakly nonuniform magnetic field. In the presence of a constant weak magnetic-field gradient the soliton quasimomentum is a linear function of time, which induces oscillatory motion of the soliton with a frequency determined by the magnetic-field gradient; the phenomenon is similar to Bloch oscillations of an electron in a weak electric field. An explicit description of soliton oscillations in the presence of a weak magnetic-field gradient is given in the adiabatic approximation. Two turning points are found in the motion of the soliton and the varieties of bounded and unbounded soliton motion are discussed. The Landau-Lifshitz equations are solved numerically for the case of a soliton moving in a weakly nonuniform magnetic field. The soliton is shown to emit a low-intensity spin wave near one of the turning points due to violation of the adiabatic approximation, and the necessary conditions for such an approximation to hold are established.

Radiation damage produced by channeled heavy ions and relativistic electrons has been considered in terms of Lindhard's basic concepts. Computer simulations as well as analytical estimates agree with the experimental data.

This review is devoted to a systematic exposition of theoretical and experimental results related to the physics of cylindrical magnetic domains (bubbles). The stability problem is discussed for an individual cylindrical domain and for a lattice of such domains, with allowance for the effect of the coercivity on the stability and dynamics of cylindrical domains. A detailed discussion is given of the laws of motion of cylindrical magnetic domains under the influence of inhomogeneities of magnetic field, temperature, and plate thickness. Phase transitions in a lattice of domains are considered, and the singularities of the magnetization and magnetic susceptibility in such phase transitions are determined. A theory is given for waves propagated in a lattice of domains. Detailed consideration is given to the effect of external factors and of the parameters of the magnetic material on the dynamical properties of a lattice of domains.

Results are given on the superconducting transition temperature and static magnetic susceptibility of U6Fe0.98 after irradiation. The relation of the reduction of Tc with neutron dose and the dose independency of the susceptibility are arguments in favour of the assignment of the decrease of Tc to the amorphization of the intermetallic compound. Es werden die Ergebnisse mitgeteilt, die nach Bestrahlung fur die Supraleitungsubergangstemperatur und statische magnetischc Suszeptibilitat von U6Fe0.98 beobachtet werden. Die Verringerung von Tc mit der Neutronendosis und die Dosisunabhangigkeit der Suszeptibilitat sind Argumente, die die Zuordnung der Verringerung von Tc zur Amorphisierung der intermetallischen Verbindung nahelegen.

One source of fluctuations in the point defect concentrations in metals arises from cascades of atomic collisions resulting from irradiation by fast neutrons and heavy ions. These randomly appearing concentrations diffuse to form fluctuating concentration fields of interstitials and vacancies. In this paper the space-time correlations of the fluctuations in point defect concentrations are investigated and the probability distribution functions of the concentrations, which may be used to determine the mean values of the physical properties with nonlinear dependence on the radiation defect concentrations, are calculated.