We report giant magnetoresistance (MR) effect that appears under the influence of optical radiation in common planar device built on Fe/SiO2/p-Si hybrid structure. Our device is made of two Schottky diodes connected to each other by the silicon substrate. Photo-induced MR is positive and the MR ratio reaches the values in excess of 104%. The main peculiarity of the MR behavior is its strong dependence on the magnitude and the sign of the bias current across the device and, most surprisingly, upon polarity of the magnetic field. To explain such unexpected behavior of the MR, one needs to take into account contribution of several physical mechanisms. The main contribution comes from the existence of localized interface states at the SiO2/p-Si interface, which provide the spots for the photo-current conduction by virtue of the sequential tunneling through them or thermal generation and optical excitation of mobile charges. External magnetic field changes the probability of these processes due to its effect on the energy states of the conduction centers. Two possible mechanisms that may be responsible for the observed dependence of magneto-resistance on the field polarity are discussed: the effect of the Lorentz force on moving carriers and spin splitting of electrons moving in the electrostatic potential gradient (Rashba effect). The most significant observation, in our opinion, is that the observed MR effect is seen exclusively in the subsystem of minority carriers transferred into non-equilibrium state by optical excitation. We suggest that building such magneto-sensitive devices based on this mechanism may set a stage for new types of spintronic devices to emerge.

Extremely large magnetoresistance induced by optical irradiation in the Fe/SiO2/p-Si hybrid structure with Schottky barrier

Reappraisal of Conduction and Hall Effect Due to Impurity Hubbard Bands in Weakly Compensated n‐GaAs

Dielectric relaxation in nanopillar NiFe–silicon structures in high magnetic fields

We explore the dielectric relaxation properties of NiFe nanowires in a nanoporous silicon template. Dielectric data of the NiFe-silicon structure show a strong relaxation resonance near 30K. This system shows Arrhenius type of behavior in the temperature dependence of dissipation peaks vs. frequency. We report magnetic field dependence of dipolar relaxation rate and the appearance of structure in the dielectric spectrum related to multiple relaxation rates. A magnetic field affects both the exponential prefactor in the Arrhenius formula and the activation energy. From this field dependence we derive a simple exponential field dependence for the prefactor and linear field approximation for the activation energy which describes the data. We find a significant angular dependence of the dielectric relaxation spectrum for regular silicon and nanostructured silicon vs. magnetic field direction, and describe a simple sum-rule that describes this dependence. We find that although similar behaviour is observed in both template and nanostructured materials, the NiFe-silicon shows a more complex, magnetic field dependent relaxation spectrum.

Dielectric Relaxation in Nanopillar NiFe-Silicon Structures in High Magnetic Fields

Giant magnetoresistance in Fe/SiO2/p-Si hybrid structure under non-equilibrium conditions

Admittance measurements on an n - -type GaAs/Al x Ga 1-x As/n + -type GaAs heterostructure (an Al x Ga 1-x As capacitor) are used to study the dependence of the activation energy for ac transport, E I , on magnetic field B. The capacitor studied has a substrate doping N s ∼7×10 15 cm -3 , which is about one-half the doping for the metal-insulator transition in n-type GaAs

Hickmott Tw

Papers

Admittance measurements of magnetic freezeout in n--type GaAs.