Optical and ESR analysis of the Fe acceptor in InP

Photoluminescence (PL), optical absorption, and electron spin resonance (ESR) have been applied to detect the different charge states of substitutional Fe in InP. The 3d⁶ one electron trap state is detected by the PL and optical absorption lines of the ⁵T₂?⁵E transitions, whereas the 3d⁵ neutral acceptor state is identified by its characteristics S = 5/2 ESR signal.     

Magnetic domain walls and pulsed magnetization reversal in amorphous Fe40Ni40P14B6 ribbon under tension

Magnetization reversal has been studied in long ribbons of Metglas 2826 under tension. At low fields propagating head-on domain boundaries of the Sixtus-Tonks type were observed. Measurements of their lengths, of order 20 to 50 cm, together with a simple magnetostatic model of their structure, yield values of the specific domain wall surface energy γ = 3.8 × 10^-8 σ^1/2 J m^-2 for tensile stress σ Pa. A value A= 5.6 × 10^-12 J m^-1 for the exchange constant follows. The low-fi eld mobility of these domain walls shows no evidence of relaxation damping at speeds below 1.2 m s^-1. The threshold field at which reverse domains nucleate is found to be proportional to the square root of the tension. At high fields (>200 A m^-1) the rough surface of the ribbon (the surface that came in contact with the quenching wheel during manufacture) reverses first and saturates at about the same time as the smooth surface begins to reverse and the volume reversal rate peaks. A simple quantitative model of the high field reversal process satisfactorily predicts both the surface and volume reversal rates. It yields a consistent value β_R = 14 kg m^-2s^-1 for the relaxation damping constant at wall speeds in excess of 13 m s^-1 and estimates the number of reversal nuclei in accord with Yagi and Anayama.     

Spin dynamics for 2d Heisenberg antiferromagnets with combined easy-plane and Dzyaloshinsky interactions

We investigate the spin dynamics of the classical two-dimensional easy-plane Heisenberg antiferromagnet with an additional Dzyaloshinsky interaction, which serves as a simple model for Langmuir-Blodgett films of Mn (C₁₈H₃₅O₂)₂. By mapping the system onto a pure easy-plane model we discuss the corresponding spin wave and vortex dynamics. The additional Dzyaloshinsky interaction forces all spins to cant in a certain direction, which is the same for neighboring spins on different sublattices. This canting causes the presence of a second spin wave peak in the dynamical in-plane correlation function below the Kosterlitz-Thouless transition temperature T_KT and a second vortex central peak above T_KT. Using a vortex gas approach we explicitly calculate the contribution of the free vortices to several dynamical correlation functions. These results are compared to a combined Monte Carlo-Molecular Dynamics simulation on square lattices with different sizes. We also discuss the relevance of this simple model for describing the spin dynamics of Mn (C₁₈H₃₅O₂)₂.     

High-pT pion production in ππ interactions

Charged pion production in high energy π^-π^- interactions is studied in the p_T region of 1–2 GeV/c. The characteristics of pion production in π^-π^- interactions are compared with those in π^-p and pp interactions. The p_T dependence of pion production in these reactions follows a systematic trend which indicates that high-p_T pion production for ππ interactions as well as for πp and pp interactions proceeds via quark-quark scattering as predicted by QCD.