Laser-induced changes of nonlinear electronic transport properties in La0.75Ba0.25MnO3 and (La0.6Pr0.4)0.67Ca0.33MnO3

We report photoinduced effects in nonlinear third harmonic ac electric transport-which is a measure for the density of correlated polarons-in thin films of [Formula: see text] (LBMO) and [Formula: see text] (LPCMO) manganites. Both materials show an enhancement of third harmonic voltage in the vicinity of the metal-to-insulator transition, indicating strong electron-lattice correlations within a phase-separated state. Relatively low laser excitation with a pulse fluence of [Formula: see text] leads to an increase (decrease) in nonlinearity in LBMO (LPCMO). With a high pulse fluence of 8mJ cm^-2, we were also able to suppress the correlations in LBMO, which is accompanied by a decrease of third harmonic voltage by [Formula: see text] in our time-averaging measurement technique.

Long-lived ultrafast spin precession in manganese alloys films with a large perpendicular magnetic anisotropy

Spin precession with frequencies up to 280 GHz is observed in Mn(3-δ)Ga alloy films with a perpendicular magnetic anisotropy constant K(u)∼15  M erg/cm(3). The damping constant α, characterizing macroscopic spin relaxation and being a key factor in spin-transfer-torque systems, is not larger than 0.008 (0.015) for the δ=1.46 (0.88) film. Those are about one-tenth of α values for known materials with large K(u). First-principles calculations well describe both low α and large K(u) for these alloys.

Energy equilibration processes of electrons, magnons, and phonons at the femtosecond time scale

We relate the energy dissipation processes at the femtosecond (electron-spin relaxation time tau el-sp) and nanosecond time scale (Gilbert relaxation taualpha) to the microscopic model proposed by Koopmans [Phys. Rev. Lett. 95, 267207 (2005)]. At both time scales, Elliot-Yafet scattering is proposed as the dominant contribution. We controllably manipulate the energy dissipation by transition metal doping (Pd) and rare earth doping (Dy) of a Permalloy film. While a change in taualpha of more than a factor of 2 is observed, tau el-sp remains constant. We explain the discrepancies as due to relaxation channels not considered in the model.