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Zeeman Splitting Caused by Localized sp-d Exchange Interaction in Ferromagnetic GaMnAs Observed by Magneto-Optical Characterization

Tanaka, Hiroki
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1441982108

Abstract Details

2015, Doctor of Philosophy (PhD), Ohio University, Electrical Engineering & Computer Science (Engineering and Technology).
The field of spintronics is considered as the next generation of spin-based electronics rather than the flow of charges utilized in electronics. It is expected that it will have some advantages in areas of information storage densities, switching speed, power consumption, manufacturing costs and others. One of the alternatives in developing a successful spintronics materials is the transition metal (TM)-doped III-V diluted magnetic semiconductors (DMSs) and GaMnAs is the proto-type ferromagnetic DMSs. Currently, the origin of ferromagnetism in GaMnAs is not fully clarified yet due to the complexity of an electronic band structure after doping of the Mn into GaAs. However, the magneto-optical characterization, especially, magnetic circular dichroism (MCD), is a very powerful technique to investigate DMS because one can obtain the information of the electronic band structure. Thus, we have performed systematic investigations of the MCD spectra and optical absorption spectra of the Ga1-xMnxAs with different concentrations of Mn. In this project, we have conducted the measurement using the transmission-mode MCD, the reflection-mode MCD and the magneto-optical Kerr effect (MOKE) for three different kinds of GaMnAs samples fabricated with the same growth conditions; GaMnAs on sapphire, GaMnAs on InP, and free-standing GaMnAs, respectively. We have successfully estimated the Zeeman splitting energy of both L (E1 and E1+delta1) and G (E0 and E0+delta0) critical points (CPs) for these materials. We utilized an energy derivative of the Gaussian function to decompose the MCD spectrum into the impurity band (IB) related background and two dispersion components around L-CPs which are expected in theory. Then, using the rigid band shift model we calculated the Zeeman splitting energy of E1 (L-CP). The Zeeman splitting energy at E1 (L-CP) was estimated to be larger than ~ 4 meV in Ga0.97Mn0.03As on sapphire, ~ 0.6 meV in Ga0.97Mn0.03As on InP, and ~ 6.5 meV in free-standing Ga0.97Mn0.03As measured at 6 K. To calculate the Zeeman splitting energy at E0 (Ganma-CP), an experimentally reported parameter of a II-VI paramagnetic DMS, Cd1-xMnxTe, was used due to some similarities of their electronic band structure. The Zeeman splitting energy at E0 (Ganma-CP) of Ga0.97Mn0.03As on sapphire, Ga0.97Mn0.03As on InP, and free-standing Ga0.97Mn0.03As was ~ 64 meV, ~ 9.6, meV and ~ 104 meV at 6 K. In addition, we found that MCD spectra around L-critical points shifted toward lower energy whereas the corresponding absorption spectra did not shift toward lower energy with an increase of Mn concentration. These results indicate that the sp-d exchange interaction in Ga1-xMnxAs has a very localized nature, because MCD is only active in a region where a band structure is affected by Mn spins, and optical absorption results from the overall sample response. This means that the sp-d exchange interactions are only generated within the sphere of influence.
Wojciech Jadwisienczak (Advisor)
Savas Kaya (Committee Member)
Avinash Kodi (Committee Member)
Faiz Rahman (Committee Member)
Martin Kordesch (Committee Member)
Arthur Smith (Committee Member)
232 p.
Chemical Engineering; Engineering; Materials Science; Optics; Physics
GaMnAs; Ferromagnetic; DMS; diluted magnetic semiconductor; MCD; MOKE; magnetic circular dichroism, magneto-optical Kerr effect; III-V; II-VI; spintronics; semiconductor; magnetic; sp-d exchange interaction; Zeeman splitting;

Recommended Citations

Citations

  • Tanaka, H. (2015). Zeeman Splitting Caused by Localized sp-d Exchange Interaction in Ferromagnetic GaMnAs Observed by Magneto-Optical Characterization [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1441982108

    APA Style (7th edition)

  • Tanaka, Hiroki. Zeeman Splitting Caused by Localized sp-d Exchange Interaction in Ferromagnetic GaMnAs Observed by Magneto-Optical Characterization. 2015. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1441982108.

    MLA Style (8th edition)

  • Tanaka, Hiroki. "Zeeman Splitting Caused by Localized sp-d Exchange Interaction in Ferromagnetic GaMnAs Observed by Magneto-Optical Characterization." Doctoral dissertation, Ohio University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1441982108

    Chicago Manual of Style (17th edition)

ohiou1441982108
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