Studies of the Faraday rotation in epitaxially grown films.

摘要

Measurements of the Faraday rotation have been made, as a function of thickness, applied magnetic field, and crystal orientation, for light of wavelength 5461A in films of nickel 100 to 400A in thickness. Reviews are given of the phenomenon of the Faraday rotation with particular reference to ferromagnetic films; of epitaxy, especially of metallic layers; and of thin film ferromagnetism. Techniques were developed with the aim of producing nickel specimens in the form of pure, parallel-sided, monocrystalline films, so as to obtain measurements which were true properties of the nickel lattice Using electron microscopy and diffraction, conditions were established for the epitaxial growth of nickel by condensation from the vapour phase in vacuo, on the principal planes of rock salt and copper. Oriented films grown on rock salt were generally aggregated or discontinuous, prominently twinned on {111} planes, and contained numerous crystal faults. Films grown on (110) faces displayed features attributable to twinning on (111) and (111) planes, and an elongation of the crystallites in the 001 direction. Oriented films grown on coppersubstrates were continuous down to 100A thickness and relatively free from faults.The magneto-optic rotations were measured by means of a photoelectric polarimeter with a precision of better than 1/3'. The construction and use of the instrument are described in the thesis. Film thicknesses were determined by measurement of the area and mass of each film, assuming bulk density. A discontinuity in the graph of rotation versus applied magnetic field for films grown on copper was found to be explicable in terms of the bulk lattice properties. No significant dependence of rotation on thickness was observed for such films. The specific rotations for the 100, 110, and 111 directions were found to be respectively +79,000 + 2,000/cm.,+88,000+ - 3,000/cm., and+97,000+ 3,000/cm.