Squid-magnetometry on ferromagnetic Ni-nanowires embedded in oriented porous silicon channels

Abstract Porous silicon is fabricated by an electrochemical etching process in aqueous HF-solution. Using appropriate etching parameters perpendicularly oriented pores are formed. In a second electrochemical process nickel is incorporated which forms a ferromagnetic bimodal nanocomposite of both needles of average diameter ≈10 nm with a large (1000:1) length-to-diameter (aspect) ratio and near-spherical nickel granules of much larger diameter (≈300 nm). Magnetic dipole interaction between needles and granules induces an easy-axis orientation perpendicular to the surface with a concomitant two-fold switching of the magnetic hysteresis at magnetic fields of 500 Oe and of 52 kOe, respectively. Characterization and magnetic investigation of the samples are carried out by scanning electron microscopy, Auger spectroscopy and SQUID-magnetometry.