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We report on an enhancement of the Curie temperature in GaMnAs/InGaMnAs superlattices grown by low-temperature molecular beam epitaxy, which is due to thin InGaMnAs or InGaAs films embedded into the GaMnAs layers. The pronounced increase of the Curie temperature is strongly correlated to the In concentration in the embedded layers. Curie temperatures up to 110 K are observed in such structures compared to 60 K in GaMnAs single layers grown under the same conditions. A further increase in T$_C$ up to 130 K can be achieved using post-growth annealing at temperatures near the growth temperature. Pronounced thickness fringes in the high resolution X-ray diffraction spectra indicate good crystalline quality and sharp interfaces in the structures.
We provide experimental evidence that the upper limit of ~110 K commonly observed for the Curie temperature T_C of Ga(1-x)Mn(x)As is caused by the Fermi-level-induced hole saturation. Ion channeling, electrical and magnetization measurements on a ser
We report on detailed investigations of the electronic and magnetic properties of ferromagnetic GaMnAs layers, which have been fabricated by low-temperature molecular-beam epitaxy. Superconducting quantum interference device measurements reveal a dec
We present a comparative, theoretical study of the doping dependence of the critical temperature $T_C$ of the ferromagnetic insulator-metal transition in Gd-doped and O-deficient EuO, respectively. The strong $T_C$ enhancement in Eu$_{1-x}$Gd$_x$O is
We have studied the magnetic properties of (GaMnAs)m/(GaAs)n superlattices with magnetic GaMnAs layers of thickness between 8 and 16 molecular layers (ML) (23-45 AA), and with nonmagnetic GaAs spacers from 4 ML to 10 ML (11-28 AA). While previous rep
Mn_5Ge_3C_x films with x>0.5 were experimentally shown to exhibit a strongly enhanced Curie temperature T_C compared to Mn_5Ge_3. In this letter we present the results of our first principles calculations within Greens function approach, focusing on