Detection of femtosecond spin voltage pulses in a thin iron film.

We present experimental evidence of a spin voltage-a difference between the chemical potentials of the two spin directions-in a thin iron film based on spin- and time-resolved photoemission spectroscopy. This voltage is the driving force for a spin current during the ultrafast demagnetization of the sample. The observed magnitude is on the order of 50 mV, a value that is quite consistent with predictions based on particle conservation and persists for approximately 100 fs.

Compact setup for spin-, time-, and angle-resolved photoemission spectroscopy.

We present a compact setup for spin-, time-, and angle-resolved photoemission spectroscopy. A 10 kHz titanium sapphire laser system delivers pulses of 20 fs duration, which drive a high harmonic generation-based source for ultraviolet photons at 21 eV for photoemission. The same laser also excites the sample for pump-probe experiments. Emitted electrons pass through a hemispherical energy analyzer and a spin-filtering element. The latter is based on spin-polarized low-energy electron diffraction on an Au-passivated iridium crystal. The performance of the measurement system is discussed in terms of the resolution and efficiency of the spin filter, which are higher than those for Mott-based techniques.

Detection of femtosecond spin injection into a thin gold layer by time and spin resolved photoemission.

The ultrafast demagnetization effect allows for the generation of femtosecond spin current pulses, which is expected to extend the fields of spin transport and spintronics to the femtosecond time domain. Thus far, directly observing the spin polarization induced by spin injection on the femtosecond time scale has not been possible. Herein, we present time- and spin-resolved photoemission results of spin injection from a laser-excited ferromagnet into a thin gold layer. The injected spin polarization is aligned along the magnetization direction of the underlying ferromagnet. Its decay time depends on the thickness of the gold layer, indicating that transport as well as storage of spins are relevant. This capacitive aspect of spin transport may limit the speed of future spintronic devices.

Estudio clínico radiológico de las fracturas esternales en edad pediátrica / Clinical and radiological study of sternal fractures in pediatrics

Las fracturas esternales se consideran infrecuentes en la edad pediátrica. Clásicamente se han descrito como fracturas secundarias a traumatismos de alta energía y con riesgo de lesiones asociadas. Objetivo: Describir los aspectos clínicos y de imagen de las fracturas esternales en niños menores de 18 años. Material y métodos: Se realiza una revisión retrospectiva de 79 pacientes pediátricos con diagnóstico de fractura esternal tras traumatismo. Resultado: Demostramos que en el 92,4% de los casos, las fracturas son causadas por mecanismos de baja energía y que únicamente en 3 (4%) pacientes se presentan lesiones asociadas. Conclusión: Nuestros resultados sugieren que las fracturas esternales en niños son frecuentemente causadas por traumatismo menor, con escasa incidencia de lesiones asociadas

Sternal fractures are considered uncommon in pediatric patients. Classically, they have been described as fractures secondary to high-energy trauma that have a risk of associated lesions. Objective: To describe the clinical and imaging features of sternal fractures in patients less than 18 years of age. Material and methods: We retrospectively reviewed 79 pediatric patients diagnosed with sternal fractures after trauma. Results: We found that 92.4% of the fractures were caused by low-energy trauma and that associated lesions were present in only 3 (4%) patients. Conclusion: Our results suggest that sternal fractures in children are often due to lesser trauma and that associated lesions are rare

Clinical and radiological study of sternal fractures in pediatrics. / Estudio clínico radiológico de las fracturas esternales en edad pediátrica.

Sternal fractures are considered uncommon in pediatric patients. Classically, they have been described as fractures secondary to high-energy trauma that have a risk of associated lesions. OBJECTIVE: To describe the clinical and imaging features of sternal fractures in patients less than 18 years of age. MATERIAL AND METHODS: We retrospectively reviewed 79 pediatric patients diagnosed with sternal fractures after trauma. RESULTS: We found that 92.4% of the fractures were caused by low-energy trauma and that associated lesions were present in only 3 (4%) patients. CONCLUSION: Our results suggest that sternal fractures in children are often due to lesser trauma and that associated lesions are rare.

Early Stages of Ultrafast Spin Dynamics in a 3d Ferromagnet.

Prior to the development of pulsed lasers, one assigned a single local temperature to the lattice, the electron gas, and the spins. With the availability of ultrafast laser sources, one can now drive the temperature of these reservoirs out of equilibrium. Thus, the solid shows new internal degrees of freedom characterized by individual temperatures of the electron gas T_{e}, the lattice T_{l} and the spins T_{s}. We demonstrate an analogous behavior in the spin polarization of a ferromagnet in an ultrafast demagnetization experiment: At the Fermi energy, the polarization is reduced faster than at deeper in the valence band. Therefore, on the femtosecond time scale, the magnetization as a macroscopic quantity does not provide the full picture of the spin dynamics: The spin polarization separates into different parts similar to how the single temperature paradigm changed with the development of ultrafast lasers.

Erratum: "Ultrafast demagnetization by hot electrons: Diffusion or super-diffusion?" [Struct. Dyn. 3, 055101 (2016)].

[This corrects the article DOI: 10.1063/1.4964892.].

Ultrafast demagnetization by hot electrons: Diffusion or super-diffusion?

Ultrafast demagnetization of ferromagnetic metals can be achieved by a heat pulse propagating in the electron gas of a non-magnetic metal layer, which absorbs a pump laser pulse. Demagnetization by electronic heating is investigated on samples with different thicknesses of the absorber layer on nickel. This allows us to separate the contribution of thermalized hot electrons compared to non-thermal electrons. An analytical model describes the demagnetization amplitude as a function of the absorber thickness. The observed change of demagnetization time can be reproduced by diffusive heat transport through the absorber layer.