20 research outputs found
Dzyaloshinskii-Moriya-type interaction and Lifshitz invariant in Rashba 2D electron gas systems
The origin of chiral magnetic structures in ultrathin films of magnetic
metals is analyzed. It is shown that the Lifshitz-type invariant term in the
macroscopic thermodynamic potential can be derived from spin-orbit Rashba
Hamiltonian in two dimensional electron gas (2DEG). The former is the
prerequisite for existence of spin cycloid, skyrmions and other chiral
phenomena observed in thin films. The estimation of the period of spin cycloid
gives the value of an order of 10 nm that agrees well with the results of
scanning probe microscopy observation reported in the literature
Novel Magnetic Photonic Crystal Structures for Magnetic Field Sensors and Visualizers
Optimized one-dimensional (1-D) magnetophotonic crystals greatly increase the sensitivity of magnetooptical sensors, which are widely used in magnetooptical imaging to observe the magnetic domain patterns in magnetic materials, to observe the vortex states in superconductors, to detect small bits in magnetooptical recording media, to visualize defects in ferromagnetic objects, and to measure the value and spatial distribution of stray magnetic fields. This paper examines the properties of such devices operating in the optimized reflection (doubled Faraday rotation) mode and discusses the use of 1-D magnetophotonic crystals as sensors
Unusual magnetoelectric effect in paramagnetic rare-earth langasite
Violation of time reversal and spatial inversion symmetries has profound
consequences for elementary particles and cosmology. Spontaneous breaking of
these symmetries at phase transitions gives rise to unconventional physical
phenomena in condensed matter systems, such as ferroelectricity induced by
magnetic spirals, electromagnons, non-reciprocal propagation of light and spin
waves, and the linear magnetoelectric (ME) effect - the electric polarization
proportional to the applied magnetic field and the magnetization induced by the
electric field. Here, we report the experimental study of the holmium-doped
langasite, HoLaGaSiO, showing a puzzling combination
of linear and highly non-linear ME responses in the disordered paramagnetic
state: its electric polarization grows linearly with the magnetic field but
oscillates many times upon rotation of the magnetic field vector. We propose a
simple phenomenological Hamiltonian describing this unusual behavior and derive
it microscopically using the coupling of magnetic multipoles of the rare-earth
ions to the electric field.Comment: 8 pages, 3 figure
On the problem of coexistence of the weak ferromagnetism and the spin flexoelectricity in multiferroic bismuth ferrite
On the example of the prototypical multiferroic bismuth ferrite the microscopic origin of the spin flexoelectricity responsible for the spin cycloid ordering is analyzed. It is shown how the three basic structural distortions corresponding to the frozen-phonon modes of an ideal perovskite lattice result in the coexistence of the spin canting and the spin cycloidal ordering. On the basis of a simple formula for the antisymmetric Dzyaloshinskii-Moriya superexchange the inhomogenous magnetoelectric contribution to the theromodynamic potential is derived and the values of the microscopic parameters corresponding to the spin canting and the spin cycloid are determined