Shape-induced phenomena in the finite size antiferromagnets

It is of common knowledge that the direction of easy axis in the finite-size ferromagnetic sample is controlled by its shape. In the present paper we show that a similar phenomenon should be observed in the compensated antiferromagnets with strong magnetoelastic coupling. Destressing energy which originates from the long-range magnetoelastic forces is analogous to demagnetization energy in ferromagnetic materials and is responsible for the formation of equilibrium domain structure and anisotropy of macroscopic magnetic properties. In particular, crystal shape may be a source of additional uniaxial magnetic anisotropy which removes degeneracy of antiferromagnetic vector or artificial 4th order anisotropy in the case of a square cross-section sample. In a special case of antiferromagnetic nanopillars shape-induced anisotropy can be substantially enhanced due to lattice mismatch with the substrate. These effects can be detected by the magnetic rotational torque and antiferromagnetic resonance measurements.Comment: 7 pages, 5 figures, to appear in Phys. Rev. B, v.75, N17, 200

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

Ion-Acoustic Solitons in Bi-Ion Dusty Plasma

The propagation of ion-acoustic solitons in a warm dusty plasma containing two ion species is investigated theoretically. Using an approach based on the Korteveg-de-Vries equation, it is shown that the critical value of the negative ion density that separates the domains of existence of compressi- on and rarefaction solitons depends continuously on the dust density. A modified Korteveg-de Vries equation for the critical density is derived in the higher order of the expansion in the small parameter. It is found that the nonlinear coefficient of this equation is positive for any values of the dust density and the masses of positive and negative ions. For the case where the negative ion density is close to its critical value, a soliton solution is found that takes into account both the quadratic and cubic nonlinearities. The propagation of a solitary wave of arbitrary amplitude is investigated by the quasi-potential method. It is shown that the range of the dust densities around the critical value within which solitary waves with positive and negative potentials can exist simultaneously is relatively wide.Comment: 17 pages, 5 figure