Magnetic Linear Dichroism in the Angular Dependence of Core-Level Photoemission from (Ga,Mn)As Using Hard X Rays

We report a study of the electronic properties of the ferromagnetic semiconductor (Ga,Mn)As using magnetic linear dichroism in the angular dependence of Mn $2p$ photoemission under hard x-ray excitation. Bulk plasmon loss satellites demonstrate that the probed Mn ions are incorporated deep within the GaAs lattice, while the observed large dichroism indicates that the spectra originate from ferromagnetic substitutional Mn. Simulations of the spectra using an Anderson impurity model show that the ferromagnetic Mn $3d$ electrons of substitutional Mn in (Ga,Mn)As are intermediate between localized and delocalized.

Figure 1

Kinetic energy dependence of the normalized MLDAD for Mn $2p$ PES, which is proportional to $R_{2p,\epsilon s}{R}_{2p,\epsilon d}\sin ({\delta }_{\epsilon s}-{\delta }_{\epsilon d})/(|R_{2p,\epsilon s}{|}^2+2|R_{2p,\epsilon d}{|}^2)$. The inset gives the chiral geometry for $\widehat{\mathbf{M}}$, $\widehat{\mathbf{P}}$, and $\widehat{\mathbf{k}}$ used in the MLDAD experiment showing two different sample positions. Also shown is the MLDAD angular distribution, which is proportional to ${sin}^2\theta \sin 2\varphi$ when $\pm \widehat{\mathbf{M}}\parallel z$, $\widehat{\mathbf{P}}\parallel x$, and $\widehat{\mathbf{k}}(\theta ,\varphi )$. In the experiment, $\theta =90°$ and $\varphi =45°$.

Figure 2

Mn $2p$ HAXPES spectra for two etched ${\mathrm{Ga}}_{1-x}{\mathrm{Mn}}_x\mathrm{As}$ films with $x=1.5\%$ and 8% and for the $x=8\%$ film prior to etching. The measurements are taken at room temperature using a photon energy of 3670 eV.

Figure 3

(a) Mn $2p$ and (b) Ga $2p$ HAXPES spectra for a ${\mathrm{Ga}}_{0.92}{\mathrm{Mn}}_{0.08}\mathrm{As}$ film. The vertical dashed lines locate the positions of the $2p_{3/2}$ photoelectron peak and associated plasmon loss satellite. The horizontal lines span the 16.5 eV characteristic energy loss of the plasmon satellites. The thin line in (a) shows the satellite region of the spectrum after subtracting a linear background and enlarging by a factor of 4. The measurements are taken at room temperature with a photon energy of 3670 eV.

Figure 4

Magnetic dichroism in photoemission from (Ga,Mn)As: (a) experimental HAXPES ($\mathrm{\text{thin line}}=+\mathrm{\text{magnetization}}$, $\mathrm{\text{thin line}}=-\mathrm{\text{magnetization}}$) at normal emission, and calculation. The well-screened and poorly screened peak in the $2p_{3/2}$ structure are indicated by $A$ and $B$, respectively. (b) Experimental MLDAD ($\mathrm{\text{points}}=\mathrm{\text{normal x-ray incidence}}$, $\mathrm{\text{line}}=\mathrm{\text{normal emission}}$), and calculations for an Anderson impurity model with $V=2.5\mathrm{eV}$, a fully localized $d^5$ state, and an itinerant electron model. The calculated curves are offset for clarity. The sample temperature is 40 K and the photon energy is 4385 eV.