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(a) In a dead magnetic layer at the boundary between a ferromagnet and semiconductor, the electron spins point in random directions. Such layers reduce the spin-injection efficiency and are a major problem for electrical spin injection. (b) The spin-injection probability across a sample of gallium arsenide. The Arkansas team found that the spin-injection efficiency is over 90% in completely flat regions (blue) and drops to 16% around a step just 5 nm high (red).