Figure 2: Overview of our measurements of the anisotropy. | Nature Communications

Figure 2: Overview of our measurements of the anisotropy.

From: Artificial control of the bias-voltage dependence of tunnelling-anisotropic magnetoresistance using quantization in a single-crystal ferromagnet

Figure 2

(a) Schematic cross-sectional structure of devices A–C used in this study. From the top surface to the bottom, an Au/GaMnAs (22, 16 and 9 nm, TC=134 K) quantum well/AlAs (5 nm)/p-GaAs:Be (100 nm, p=7 × 1018 cm−3) heterostructure is fabricated on a p+-GaAs (001) substrate. The bias voltage V is applied between the Au electrode and backside of the substrate. (b) Schematic view representing the directions of the magnetization M (red arrow) of the GaMnAs layer and of the magnetic field μ0|H|=890 mT (grey arrow) applied in our measurements. (c,d) Schematic valence band (VB) diagrams of the tunnel devices when negative (c) and positive (d) V are applied. The black solid and red dash-dotted lines represent the top of the VB and the quasi Fermi levels EF, respectively. The blue dash lines represent the quantized VB levels in the GaMnAs layer. These quantum levels are formed because the VB holes are confined by the surface Schottky barrier (∼1 nm) and AlAs layer27,28. The grey, blue and pink regions represent the band gap, VB and impurity band (IB), respectively. The red arrow represents the tunnel direction of the holes when V is applied. The character q represents the elementary charge.

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