RESUMEN
In this work, we describe an experimental setup for a spatially resolved pump-probe experiment with an integrated wide-field magneto-optical (MO) microscope. The MO microscope can be used to study ferromagnetic materials with both perpendicular-to-plane and in-plane magnetic anisotropy via polar Kerr and Voigt effects, respectively. The functionality of the Voigt effect-based microscope was tested using an in-plane magnetized ferromagnetic semiconductor (Ga,Mn)As. It was revealed that the presence of mechanical defects in the (Ga,Mn)As epilayer alters significantly the magnetic anisotropy in their proximity. The importance of MO experiments with simultaneous temporal and spatial resolutions was demonstrated using a (Ga,Mn)As sample attached to a piezoelectric transducer, which produces a voltage-controlled strain. We observed a considerably different behavior in different parts of the sample that enabled us to identify sample parts where the epilayer magnetic anisotropy was significantly modified by the presence of the piezoelectric transducer and where it was not. Finally, we discuss the possible applicability of our experimental setup for the research of compensated antiferromagnets, where only MO effects even in magnetic moments are present.
RESUMEN
Spin-valves or spin-transistors in magnetic memories and logic elements are examples of structures whose functionality depends crucially on the length and time-scales at which spin-information is transferred through the device. In our work we employ spatially resolved optical pump-and-probe technique to investigate these fundamental spin-transport parameters in a model semiconductor system. We demonstrate that in an undoped GaAs/AlGaAs layer, spins are detected at distances reaching more than ten microns at times as short as nanoseconds. We have achieved this unprecedented combination of long-range and high-speed electronic spin-transport by simultaneously suppressing mechanisms that limit the spin life-time and the mobility of carriers. By exploring a series of structures we demonstrate that the GaAs/AlGaAs interface can provide superior spin-transport characteristics whether deposited directly on the substrate or embedded in complex semiconductor heterostructures. We confirm our conclusions by complementing the optical experiments with dc and terahertz photo-conductivity measurements.
RESUMEN
Biopsies of orbital tumours are made as a rule by the classical surgical approach. In a 82-year-old risk patient the authors chose, however, the stereotactic method of collection of pathological tissue from the orbit and this non-traditional procedure, using special instruments, proved unpretentious and successful.