Events

Department of Magnetic Reseach Seminar

Segregation of magnetic MnAs nanocrystals in MBE-grown (Ga,Mn)As dilute ferromagnetic semiconductor layers, superlattices and nanowires

dr hab. Janusz Sadowski, prof. IF PAN

Instytut Fizyki Polskiej Akademii Nauk w Warszawie

Seminarium odbędzie się zdalnie w aplikacji Microsoft Teams. W celu wzięcia udziału w wydarzeniu należy dołączyć do zespołu Seminarium OBM.Można do niego dołączyć na stałe przy użyciu kodu dostępu ol7omod (dotyczy to osób posiadających konto w domenie intibs.pl, pozostałe osoby proszę o kontakt z dr. hab. Adamem Pikulem ()).

Streszczenie:

Segregation of secondary magnetic phases is one of the essential problems in dilute magnetic semiconductors (DMS). In many DMS materials this issue was not recognised in the initial stages of investigations, generating unrealistic expectations concerning potential applications of DMSs in spintronic devices fully integrated with semiconducting technology. The most known examples of such materials with initially unrecognised segregation of magnetic nano-precipitates are Mn-doped GaN, ZnO, and Cr-doped ZnTe. Only few materials, such as Mn-doped narrow bandgap IV-VI semiconductors, e.g. (Pb,Sn,Mn)Te, (Ge,Mn)Te; and Mn-doped III-V arsenides (Ga,Mn)As, (In,Mn)As survived as DMSs with carrier mediated intrinsic ferromagnetic properties occurring up to relatively high temperatures, exceeding 100 K (except (Pb,Sn,Mn)Te with much lower temperature limit of about 20 K). In (Ga,Mn)As which is the most prominent representative of ferromagnetic DMSs, the segregation of secondary magnetic phases can be induced in a controlled way. Annealing of homogeneous material to moderate/high temperatures in the range of 400 – 600 °C leads to decomposition of (Ga,Mn)As solid solution into granular system comprising MnAs nanocrystals embedded in the GaAs semiconductor host lattice. I will show how to control dimensions, densities, distribution and magnetic properties of such magnetic nanoprecipitates in GaAs in 3-dimensional (thick layers) [1], two-dimensional (superlattices) [2] and quasi one-dimensional (nanowires) [3] systems. In the latter case the significant ferromagnetic phase transition temperature increase of strained MnAs nanocrystals has been observed.

[1] J. Sadowski, et. al., Phys. Rev. B 84, 245306 (2011).

[2] J. Sadowski et. al., J. Phys.: Cond. Mat. 25, 196005 (2013).

[3] A. Kaleta, et. al., and J. Sadowski, Nano Lett. 19, 7324 (2019).