Ferromagnetism in GaAs/InAs/GaAs Quantum Dot Layer Delta-Doped with Mn

Transport, magnetotransport and magnetic properties of structures GaAs/InAs/GaAs with a InAs quantum dot (QD) layer have been investigated in the temperature interval 4.2<T<300 K. The structures were delta-doped by Mn from a one side to provide magnetic properties and by carbon from the other side to enhance a p-type conductivity. The ferromagnetic phase up to 400 K was detected by SQUID magnetometer. Anomalous Hall-effect was observed at low T. The role of additional disorder in conducting channel due to the QD layer was investigated. It is shown a principal role of a fluctuation potential of Mn layer separated from conducting QD layer by a spacer in anomalous transport properties of structures. The negative magnetoresistance was observed at low T due to the reduction of the spin-flip scattering by aligning spins by magnetic field.

ONE-LOOP QUANTUM COSMOLOGICAL CORRECTION TO THE GRAVITATIONAL CONSTANT IN THE CLOSED FRIEDMANN–ROBERTSON–WALKER UNIVERSE

In this paper, we calculate the one-loop quantum cosmological corrections to the kink energy in the closed Friedmann–Robertson–Walker universe in which the fluctuation potential V″ has a shape invariance property. We use the generalized zeta-function regularization method to implement our setup for describing quantum kink-like states. It is conjectured that the corrections lead to the renormalized gravitational constant.