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Scheme of a magnetic bipolar transistor in the forward active mode. The base has an equilibrium electron spin polarization , illustrated by the spin-split conduction band. Spin up (down) electrons are pictured as dark (light) filled circles. Holes are unpolarized. The emitter has a source of spin polarization, here shown as a circularly polarized light, giving rise to a nonequilibrium spin polarization . The direction of the currents is indicated.
The Ebers–Moll equivalent circuit of a MBT. The voltage sources are arranged for the forward active mode. The left (right) circuit is the emitter (collector). The emitter circuit has a diode for the forward current, and a current source which depends on the bias in the collector circuit. In addition, there are two new elements. A spin diode whose direction can be flipped: its filled triangle points to the forward direction when , otherwise the current direction changes. A new spin current source (dashed arrow), pointing in the direction of the current if . The direction of the current can also be flipped. Similar notation applies for the right (collector) circuit.
Operational modes of BJT’s and MBT’s. Forward (F) and reverse (R) bias means positive and negative voltage, respectively. Symbols MA and GMA stand for magnetoamplification and giant magnetoamplification, while ON and OFF are modes of small and large resistance, respectively; SPSW stands for spin switch.
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