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In this work, ballistic electron transport through the lowest miniband of a biased GaAs–AlGaAs superlattice is investigated in transverse magnetic fields. As method we employ a solid-state version of ballistic electron emission microscopy/spectroscopy using a metal-insulator-metal injector structure that replaces the tip of the scanning tunneling microscope (STM). The ballistic electron current measured as a function of the collector bias shows a peak at flatband conditions indicating coherent transport through the superlattice miniband. With increasing transverse magnetic fields, this peak is quenched and evidence of sequential LO-phonon scattering inside the superlattice is found. Using an extended transfer matrix method, the observed effects are quantitatively explained; differences to previous STM based measurements are discussed.

We present an analytical derivation of the switching field distribution (SFD) at finite temperature for a single domain particle from the Neel-Brown model in the presence of a linearly swept magnetic field. By considering the field dependence of the attempt frequency f0 in the rate equation, we find enhancement of coercivity compared to models using constant f0. The contribution of thermal fluctuations to the standard deviation of the switching field HC derived here reaches values of 10% HC. Considering this contribution, which has been neglected in previous work, is important for the correct interpretation of measurements of switching field distributions.