  we investigated the magneto-electroluminescence (MEL) in
tri-(8-hydroxyquinoline)-aluminum based organic light-emitting diodes (OLEDs)
through the steady-state and transient method simultaneously. The MELs show the
great different behaviors when we turn the driving condition from a constant
voltage to a pulse voltage. For devices driven by the constant voltage, the
MELs are similar with the literature data; for devices driven by the pulse
voltage, the MELs are quite different, they firstly increase to a maximum then
decrease as the magnetic field increases continuously. Negative MELs can be
seen when both the magnetic field and driving voltage are high enough.
