Determination of s-d exchange coupling in GaMnN by time-resolved Kerr rotation spectroscopy

Coherent electron-spin dynamics in ${\text{Ga}}_{1-x}{\text{Mn}}_x\text{N}$ has been investigated by time-resolved Kerr rotation spectroscopy. The effective electron $g$ factor shows a linear increase with the Mn concentration due to the s-d exchange coupling between the conduction electrons and the $d$-shell electrons of ${\mathrm{Mn}}^{3+}$ impurities. The magnitude and sign of the s-d exchange constant are determined precisely to be $N_0\alpha =+0.23\pm 0.02\mathrm{eV}$, indicative of a ferromagnetic s-d exchange coupling in GaMnN. The determined $N_0\alpha$ is consistent with the typical value found in most diluted magnetic semiconductors and reveals that GaMnN is indeed not an exception.

Figure 1

(a) PL spectra measured at $T=13\mathrm{K}$. The PL intensities have been normalized with respect to the ${\mathrm{FX}}_{\mathrm{A}}$ peak. (b) The energy shift of ${\mathrm{FX}}_{\mathrm{A}}$ as a function of Mn concentration. (c) The reflectivity spectrum for the $x=0.27\%$ sample.

Figure 2

(a) TRKR spectra measured at $T=15\mathrm{K}$ and $B=0.58$ T. (b) The deduced effective $g$ factor and (c) the spin lifetime $T_2^{*}$ as a function of Mn concentration.

Figure 3

Temperature-dependent TRKR spectra taken at $B=0.58$ T for (a) the undoped GaN and (b) the ${\text{Ga}}_{1-x}{\text{Mn}}_x\text{N}$ with $x=0.27$% samples.

Figure 4

The evolution of the effective electron $g$ factor with (a) the Mn concentration and (b) the temperature.