20 research outputs found
Elastic domains in antiferromagnets
We consider periodic domain structures which appear due to the magnetoelastic
interaction if the antiferromagnetic crystal is attached to an elastic
substrate. The peculiar behavior of such structures in an external magnetic
field is discussed. In particular, we find the magnetic field dependence of the
equilibrium period and the concentrations of different domains
Phase Field Modeling of Fracture and Stress Induced Phase Transitions
We present a continuum theory to describe elastically induced phase
transitions between coherent solid phases. In the limit of vanishing elastic
constants in one of the phases, the model can be used to describe fracture on
the basis of the late stage of the Asaro-Tiller-Grinfeld instability. Starting
from a sharp interface formulation we derive the elastic equations and the
dissipative interface kinetics. We develop a phase field model to simulate
these processes numerically; in the sharp interface limit, it reproduces the
desired equations of motion and boundary conditions. We perform large scale
simulations of fracture processes to eliminate finite-size effects and compare
the results to a recently developed sharp interface method. Details of the
numerical simulations are explained, and the generalization to multiphase
simulations is presented
Influence of Strain on the Kinetics of Phase Transitions in Solids
We consider a sharp interface kinetic model of phase transitions accompanied
by elastic strain, together with its phase-field realization. Quantitative
results for the steady-state growth of a new phase in a strip geometry are
obtained and different pattern formation processes in this system are
investigated
Critical Velocity in 3He-B Vibrating Wire Experiments as Analog of Vacuum Instability in a Slowly Oscillating Electric Field
The Lancaster experiments with a cylindrical wire moving in superfluid 3He-B
are discussed, where the measured critical velocity of pair creation is much
below the Landau critical velocity. The phenomenon is shown to be analogous to
the instability of the electron-positron vacuum in an adiabatically alternating
strong electric potential of both signs, where the positive- and negative-root
levels cross and thus the instability treshold is twice less than in the
conventional case of a single static potential well.Comment: RevTex file, 6 pages, 4 figure
Quantum Nucleation in a Ferromagnetic Film Placed in a Magnetic Field at an Arbitrary Angle
We study the quantum nucleation in a thin ferromagnetic film placed in a
magnetic field at an arbitrary angle. The dependence of the quantum nucleation
and the temperature of the crossover from thermal to quantum regime on the
direction and the strength of the applied field are presented. It is found that
the maximal value of the rate and that of the crossover temperature are
obtained at a some angle with the magnetic field, not in the direction of the
applied field opposite to the initial easy axis.Comment: 15 pages, RevTex, 3 PostScript figures. To appear in Phys. Rev.