Crystalline fields,exchange interactions and spin reorientations in TmxHo1−xFe2 systems,studied by a Yb170 Mössbauer probe

Mössbauer studies of the 84.3 keV gamma ray of Yb¹⁷⁰ emitted from Yb in Tm_xHo_1?xFe₂ at various temperatures were performed. These yield the crystalline field parameters (A₄〈r⁴〉 = 36 ± 5 K, A₆〈r⁶〉 = -3 ± 2K, the exchange field (μ_BH_exch = 116 ± 4 K) and the Yb³⁺ free ion hyperfine constants (H_4f = 4100 ± 150 kOe, eqQ = 2400 ± 250 MHz and H (conduction electrons) = 350±100 kOe). Spin relaxation phenomena observed in TmFe₂ at low temperatures give a value of ～ 0.03 for |?(E_F)J_sf|. Spectra observed in Tm_0.2Ho_0.8Fe₂ in the spin reorientation transition region indicate that the transition is of second order.     

Hydrodynamics of spin-polarized transport and spin pendulum

The dynamics of a nonequilibrium spin system dominated by collisions preserving the total quasimomentum of the interacting electrons and quasiparticles is considered. An analysis of the derived hydrodynamic equations shows that weakly attenuated spin-polarization waves associated with an oscillating drift current can exist in a magnetically inhomogeneous conducting ring. Spin-polarized transport in a ballistic regime of wave propagation through a conductor is also considered, and a simple method is proposed for distinguishing these waves from spin and current oscillations that develop in the hydrodynamic regime. It is shown that a potential difference arises between the leads of an open nonuniformly spin-polarized conductor as a manifestation of spin polarization of electron density. This spin-mediated electrical phenomenon occurs in both hydrodynamic and diffusive limits.     

Generation of 10(11) contrast 50 TW laser pulses

We demonstrate what we believe to be the highest-contrast (10(11)), multiterawatt, chirped-pulse amplification (CPA) Ti:sapphire laser by applying the modified cross-polarized-wave (XPW) generation method. This method produces a contrast improvement of 3 orders of magnitude using microjoule input energy. Microjoule energy can be achieved by direct amplification without the complications of a double CPA system. The 10(11) contrast is sufficient for experiments on high-damage-threshold solid targets with focused intensities up to 10(22) W/cm(2).