Spacer-dependent transport and magnetic properties of digital ferromagnetic heterostructures

Abstract

We examine the relationship between the transport and magnetic properties of digital ferromagnetic heterostructure superlattices in which 0.5 monolayer MnAs planes alternate with undoped GaAs spacer layers. The data show that as the thickness t of the GaAs spacers increases, charge transport and the Curie temperature both approach their independent-layer limits at comparable values of t. An increase in the per-layer conductivity with decreasing t accompanies a rise in TC. This behavior is consistent with an enhancement of interlayer ferromagnetic interactions by charge coupling across the spacers.

Infrared survey of the carrier dynamics in III-V digital ferromagnetic heterostructures

“…The optical properties of DFH also offer insights into the origin of the suppression of the critical temperature and development of the insulating state with increased spacer thickness. 2,3 We find that the latter effect occurs due to the diminished coupling between Ga 1−x Mn x As layers without apparent depression of the electronic spectral weight associated with the doped holes within the layers. Charge carriers become increasingly localized at y ജ 15 monolayers ͑ML͒ prompting a mobility gap, which has never previously been observed to coexist with ferromagnetism in III-V semiconductors.…”

“…1 Recently this approach was employed to create a new class of III-V, Mn doped, dilute magnetic semiconductors ͑DMS͒ that promise to advance our understanding of the interplay between dimensionality, carrier dynamics, and magnetism in this family of materials. 2,3 These phenomena are difficult to investigate using random alloys due to the multiple effects of Mn doping. Apart from generating local moments and carriers ͑holes͒, Mn introduces disorder with all these effects revealing non-trivial entanglement.…”

“…Indeed, DFHs are comprised of ␦-doped MnAs submonolayers separated by GaAs spacers of variable thickness ͑y͒. 2,3 To take full advantage of the DFH approach it is prudent to inquire into the nature of the doped layers as well as the electronic and/or magnetic coupling between them. Empowered by earlier spectroscopic studies of the Ga 1−x Mn x As random alloys 5 we demonstrate that the doped layer in DFHs posses the properties of Ga 1−x Mn x As.…”

Search for stable ferromagnets amongAIV/Fe digital alloys (AIV=Si, Ge) using first-principles calculations

“…[1][2][3][4][5][6] A DA is an example of δ doping, [7][8][9] which represents a periodic sequence of the ultrathin TM layers embedded within a semiconductor host. Such a way of preparation allows tailoring the magnetic properties of the samples freely by changing the TM atoms' concentration or semiconductor spacer thickness and can yield to high Curie temperature.…”

Interlayer exchange coupling in digital magnetic alloys

“…One example is the digital heterostructure GaAs/MnAs grown by alternate deposition of nanolayers of GaAs ͑SC͒ and MnAs ͑FM͒. 2,3 Digital alloys ͑GaAs,GaSb͒/Mn have been grown by periodically embedding submonolayers of magnetic atoms ͑Mn͒ into the SC host ͑GaAs or GaSb͒. [4][5][6] Note also the original method of ␦ doping of Mn atoms into the SC ͑GaAs͒-based heterostructures, successively achieved in Refs.…”