We trace the ultrafast dynamics of the spin density wave gap of the pnictide system BaFe2As2 probing resonantly with broadband multi-terahertz pulses. The photoexcitation in the low-temperature ground state leads to a fast suppression of the spin order followed by a slower recovery process. Surprisingly, in the normal state, we observe periodic oscillations of the spin density wave feature at a...

We study the interaction between two important features of ferromagnetic nanoparticles: magnetic domain walls and spin waves. Micromagnetic simulations reveal that magnetostatic spin waves change their phase as they pass through domain walls. Similar to an Aharonov-Bohm experiment, we suggest to probe this effect by splitting the waves on different branches of a ring. The interference of mergin...

Spin-wave excitation mode from the spin-polarized ground state in the fractional quantum Hall liquid with odd fractions (ν = 1/3, 1/5) numerically obtained by the exact diagonalization of finite systems is shown to be accurately described, for wavelengths exceeding the magnetic length, in terms of the composite-fermion mean-field approximation for the spin-wave (magnon) theory formulated in the...

We investigate the nonlinear dynamics underlying the evolution of a 2-D ferromagnetic film with uniaxial anisotropy and an oscillating magnetic field. Considering the associated Landau-Lifshitz spin evolution equation with Gilbert damping included, we study the dynamics in terms of the stereographic variable. We identify several new fixed points for suitable choice of external field. In particu...

Magnetic excitation of the iron-based superconductor parent compound BaFe2As2 at finite temperature are addressed with a first-principles formulation of the Helmholtz energy, which can account for the finite temperature mixture of many magnetic configurations. We find that it is the spin exchange coupling in the interplane c direction that dictates the spin density wave ordering. We have also q...

We have used time-resolved scanning Kerr microscopy to study spin waves in a magnetic microwire subjected to a bias magnetic field applied parallel to its long axis. The spin-wave spectra obtained from different points near one end of the wire reveal several normal modes. We found that modes of a higher frequency occupied regions located further from the end of the wire. This was interpreted in...

We study the low-energy collective excitations and dynamical response functions of weakly coupled random antiferromagnetic spin-1 /2 chains. The interchain coupling leads to Néel order at low temperatures. We use the real-space renormalization-group technique to tackle the intrachain couplings and treat the interchain couplings within the random phase approximation RPA . We show that the system...

We calculate current, spin current and tunnel magnetoresistance (TMR) for a quantum dot coupled to ferromagnetic leads in the presence of a square wave of bias voltage. Our results are obtained via time-dependent nonequilibrium Green function. Both parallel and antiparallel lead magnetization alignments are considered. The main findings include a wave of spin accumulation and spin current that ...

Using the quasiclassical Green’s function formalism, we study the influence of the odd-frequency spin-triplet superconductivity on the local density of states LDOS in a diffusive ferromagnet DF attached to a superconductor. Various possible symmetry classes in a superconductor are considered which are consistent with the Pauli’s principle: even-frequency spin-singlet even-parity ESE state, even...