Narrow Results

Ability of epitaxial perovskite oxide ferroelectric films to maintain a poled polarization state on a long-term scale is crucial for advanced devices employing such films. Here polarization relaxation with time, or aging, is experimentally studied in epitaxial capacitor heterostructures of PbTiO₃ sandwiched between SrRuO₃ and Pt electrodes. The relaxation obeys logarithmic time-decay for the time 10²–10⁵s after poling pulses. The decay is by factor $\sim$10 slower than that reported for polycrystalline films. Our experimental results show that existing models are insufficient for epitaxial films.

The cubic polymorph of the binary transition metal pnictide (TMP) MnSb, c-MnSb, has been predicted to be a robust half-metallic ferromagnetic (HMF) material with minority spin gap ≳1 eV. Here, MnSb epilayers are grown by molecular beam epitaxy (MBE) on GaAs and In_0.5Ga_0.5As(111) substrates and analyzed using synchrotron radiation X-ray diffraction. We find polymorphic growth of MnSb on both substrates, where c-MnSb co-exists with the ordinary niccolite n-MnSb polymorph. The grain size of the c-MnSb is of the order of tens of nanometer on both substrates and its appearance during MBE growth is independent of the very different epitaxial strain from the GaAs (3.1%) and In_0.5Ga_0.5As (0.31%) substrates.