Kerr Ellipticity Spectra Research Articles

Ｄｉａｍｏｎｄ及びＭｇＯ基板上のＣｕ及びＮｉ薄膜の結昌成長と磁気光学Ｋｅｒｒ効果

Ni and Cu thin films of about 100 and 50 nm were deposited on MgO(001), (110), (111), and diamond(001) substrates by using a molecular beam epitaxy (MBE) method. Their growth mechanisms were investigated by in-situ RHEED. We found that Ni films can be grown easily on a diamond(001) substrate where the lattice mismatch between Ni and diamond is very small (1.42%). We found that, despite a large lattice mismatch of 19.5% (16.5%) between Ni (Cu) and MgO, Ni and Cu films can be grown epitaxially on MgO(001), (110), and (111) substrates. Moreover we measured magneto-optical (MO) Kerr ellipticity spectra on the epitaxial Ni films on MgO and diamond substrates. As a result, no difference of MO Kerr spectra were observed on Ni(001), (110), and (111). The epitaxial Ni films with Cu buffer layers show relatively small coercive force (Hc) compared with that of epitaxial Ni films without Cu buffer layers.

Magneto-optical spectra of epitaxial ferromagnetic MnAs films grown on Si and GaAs substrates

We have studied magnetic circular dichroism (MCD) spectra of ferromagnetic MnAs epitaxial thin films of (1̄101), (1̄100), and (0001) crystallographic growth orientations. The films were grown on Si(001), Si(111), GaAs(001), and GaAs(111)B substrates by molecular-beam epitaxy. We have found strong crystal orientation dependence of MCD spectra of MnAs films in terms of characteristic features and absolute intensity of MCD signals. We have also measured temperature dependence of MCD spectra on a (0001) MnAs film. Features at low temperatures are found to be different from those at room temperature. Our experimental results are compared with the ionic model for the electronic structure of NiAs-type MnAs and with magneto-optical Kerr ellipticity spectra recently calculated using an all electron full potential linear muffin-tin orbital method.

Molecular-beam epitaxy of Mn1+xSb thin films and substrate temperature dependence of their magneto-optical properties

Ferromagnetic Mn1+xSb thin films have been grown on (001) GaAs substrates by molecular-beam epitaxy at substrate temperatures (TS) in the range from 50 to 400 °C. The excess Mn composition (x) of the grown films was found to change uniquely depending on TS. The polar magneto-optical Kerr effect measurement demonstrated a strong TS dependence of Kerr rotation and Kerr ellipticity spectra of Mn1+xSb films from the infrared through ultraviolet wavelength region. A possible origin of the TS dependence of the spectra is discussed in connection with the composition of Mn1+xSb films.

MAGNETO-OPTICAL CHARACTERIZATION OF EPITAXIALLY GROWN MANGANESE PNICTIDES

MnAs and MnSb thin films were grown on GaAs (100) substrates by hot-wall epitaxy (HWE) technique. Epitaxial growth with (10-11) axis parallel to GaAs (100) surface was observed in both films. Polar magneto-optical Kerr rotation and Kerr ellipticity spectra were measured in these samples. For MnAs, it is for the first time that reliable polar Kerr spectra were obtained.

Thickness-dependent oscillation of the magneto-optical properties of Au-sandwiched (001) Fe films.

Au-sandwiched bcc (001) Fe wedges were produced by the molecular beam epitaxy method (0--20 \AA{}). The polar Kerr rotation and Kerr ellipticity spectra (1.5--5 eV) were measured as a function of the Fe thickness d. In both kinds of spectra new peaks appear. The complex Kerr rotation oscillates as a function of the film thickness. More than four oscillations could be clearly observed in the measured thickness range. Magneto-optical transitions from the ${\mathrm{\ensuremath{\Delta}}}_{5}$ band to quantum-well states (QWS's) in the ${\mathrm{\ensuremath{\Delta}}}_{1}$ majority-spin band change the intrinsic dielectric properties. The oscillation period and transition energies are in agreement with theory. Thickness-dependent structures below 2.5 eV strongly suggest the occurrence of partially confined QWS's around ${\mathit{E}}_{\mathit{F}}$ or QWS's in the ${\mathrm{\ensuremath{\Delta}}}_{5}$ band.

Magneto-optical Kerr effect, enhanced by the plasma resonance of charge carriers.

It is shown by model calculations that the dispersion of the diagonal part of the dielectric constant near the plasma edge in a metallic crystal has a strong influence on the magneto-optical properties. The plasma edge leads to resonancelike peaks in the Kerr rotation and Kerr ellipticity spectra and to a strong enhancement of the magnitude of the Kerr effect. The sharp and very large peaks observed in the Kerr effect of several transition-metal and rare-earth compounds are not necessarily related to sharp magneto-optical transitions, but could be a result of the presence of the plasma edge at the same frequency.