The up-conversion of photoluminescence in a series of GaAs/͑ordered͒GaInP 2 heterojunctions has been investigated using high magnetic field and high pressure. Samples which exhibit this effect have been demonstrated to have a type-II band alignment and also localization centers in GaInP 2 Some samples revealing a type-I band alignment do not show this effect at atmospheric pressure. However, such a sample exhibits up-conversion under a hydrostatic pressure of 1.2 GPa. Our results establish a type-II band alignment as one of the key elements for explaining the observed up-conversion. ͓S0163-1829͑97͒50224-4͔
The first observation of a pressure-induced metallization accompanied by the spontaneous collapse of magnetic ordering is reported. This isostructural concurrence is observed in the layered antiferromagnetic insulator Nih. Electrical transport, x-ray-diffraction, and ,29 I Mossbauer studies were carried out in diamond-anvil cells. The evidence points to a mechanism by which the originally filled 5p-iodide band shifts and overlaps with the partially filled nickel-3d states. The formation of a hybridized conduction band at P > 19 GPa results in the onset of a diamagnetic metallic ground state.
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