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Fine structure of the Mn acceptor in GaAs in external deformation and magnetic field

Name
Grigorii
Surname
Dimitriev
Scientific organization
Ioffe Institute
Academic degree
Master of Science, PhD student
Position
Junior Researcher
Scientific discipline
Physics & Astronomy
Topic
Fine structure of the Mn acceptor in GaAs in external deformation and magnetic field
Abstract
We determine the electronic level structure of the Mn acceptor in bulk GaAs in presence of applied uniaxial stress and an external magnetic fi eld. Resonant spin-flip Raman scattering is used to measure the g factor of the A0Mn center in the ground and excited states and characterize the optical selection rules of the spin-flip transitions between these states. We determine the random stress fi elds near the Mn acceptor, the constant of the antiferromagnetic exchange interaction and the deformation potential for the exchange energy.
Keywords
nanostructures, diluted magnetic semiconductors, raman scattering, magneto-optics
Summary

We determine the electronic level structure of the Mn acceptor A0Mn in bulk GaAs in dependence on uniaxial stress and an external magnetic field. Different spectroscopic methods show that the presence of Mn2+ impurity leads to the formation of a complex of the valence-band hole bound to a Mn2+ ion and that the coupling between the hole and Mn spins is antiferromagnetic. This antiferromagnetic exchange leads to the formation of four levels that are described by the quantum number F = J + S = 1; 2; 3; 4 [1].

Resonant spin-flip Raman scattering is used to measure the g factor of the A0Mn center in the ground and excited states with the total angular momenta F = 1 and F = 2 and characterize the optical selection rules of the spin-flip transitions between these Mn-acceptor states.

We demonstrate that even without external stress the Mn acceptor experiences random local stress that induces a splitting of the ground F = 1 state of up to 0.7 meV. We determine the random stress fields near the Mn acceptor and the constant of the antiferromagnetic exchange interaction between the valence-band holes and the electrons of the inner Mn2+ shell. It is also shown that uniaxial compressive stress leads surprisingly to a significant reduction of the p-d exchange interaction strength and to a deformation potential value of the exchange constant given by Ap = 0.9 eV. Furthermore, the measured effective g factor of the excited F = 2 states is comparable with the theoretically predicted g = 23/12 value. The developed theoretical model of the Mn acceptor, which considers random local and external uniaxial stresses as well as a magnetic field, satisfactorily describes the observed spin-flip Raman lines and their polarization characteristics. This model highlights that the previously reported value ΔF1-F2 of the hole-Mn-ion exchange energy was underestimated by about 20%. By combining the experimental Raman study with the developed theoretical model on the scattering efficiency the fine structure of the Mn acceptor for the multiplets with the total angular momenta F = 1 and F = 2 is determined in full detail.

Our study on the spin-flip Raman scattering of the Mn acceptors in GaAs underlines that their individual properties are essential to explain the stress dependence of the antiferromagnetic hole-Mn exchange interaction. These results may be considered as a step toward understanding the magnetic anisotropy of (Ga,Mn)As as a result of the individual Mn acceptors and may be employed for other acceptor complexes in III-V semiconductor structures.

[1] N.S. Averkiev, et al, Soviet Phys. Semiconductors, 1987