Ferromagnetic Interfacial Interaction and the Proximity Effect in a ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ Bilayer

The magnetic properties of a ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer epitaxied on GaAs (001) are studied both experimentally and theoretically. Unlike the common antiferromagnetic interfacial interaction existing in most ferromagnet-magnetic semiconductor bilayers, a ferromagnetic interfacial interaction in the ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer is observed from measurements of magnetic hysteresis and x-ray magnetic circular dichroism. The Mn ions in a 1.36 nm thick (Ga,Mn)As layer remain spin polarized up to 400 K due to the magnetic proximity effect. The minor loops of the ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer shift with a small ferromagnetic interaction field of $+24\mathrm{Oe}$ and $-23\mathrm{Oe}$ at 15 K. The observed ferromagnetic interfacial coupling is supported by ab initio density functional calculations. These findings may provide a viable pathway for designing room-temperature semiconductor spintronic devices through magnetic proximity effect.

Figure 1

A DCXRD curve of a ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer. The left inset is the HRTEM image and the right inset is a close-up view around the (Ga,Mn)As (004) peak.

Figure 2

Temperature dependence of the remanent magnetization of the ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer and the single (Ga,Mn)As layer along the [110] and [$-110$] directions.

Figure 3

Magnetic hysteresis of a ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer at 15, 150, and 300 K. The magnetic field was along the [110] (a) and [$-110$] directions (b). The insets are close-ups around a zero magnetic field.

Figure 4

Minor loops of a ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer and major loop of a (Ga,Mn)As reference sample at 15 K along the [110] direction.

Figure 5

XMCD spectra of (a) Mn $L_{2,3}$ of the single (Ga,Mn)As layer and ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer; (b) Co $L_{2,3}$ and (c) Fe $L_{2,3}$ of ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer at different temperatures. (d) XMCD loops of Mn (square), Co (circle), and Fe (triangle) of the ${\mathrm{Co}}_2\mathrm{FeAl}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ bilayer at 400 K.