Dong-Liang Qian

STUDY OF THE KERR EFFECT OF COXAG100-X GRANULAR FILMS

A series of CoxAg100−x granular films was annealed at 100, 250, 400, and 500 °C, respectively. Both the dielectric function and polar Kerr effect were measured using a spectroscopic ellipsometer and a magneto-optical Kerr spectrometer in the 1.5–4.5 eV photon energy range. It was found that the Kerr effect was greatly enhanced with increasing annealing temperature, especially for those samples having low Co compositions. After annealing, the strong resonance peaks appear in the 3.7–4.1 eV range. For the typical sample with x=6, the maximum Kerr rotation angle is about 0.26° near 4.0 eV after annealing at 500 °C. Through data analysis, the large negative peak at about 3.85 eV is attributed to the plasma edge of Ag, and the positive peak near 4.0 eV is attributed to the new magneto-optical structure and the properties of the granular film. The larger short-wavelength Kerr effect will be useful for increasing magneto-optical data-storage density.

The effect of interference on magneto-optics in magneto-optical layered structures

In this article the magneto-optics of magneto-optical (M-O) layered structures have been studied theoretically and experimentally. For the air/M-O/air configuration, an analytic expression between the apparent complex Faraday rotation and the eigenvalue φF=e1φF′ can be obtained, when the M-O layers are semitransparent and weakly magnetic. The interference factor e1 is a function of the optical constants and the M-O layer thickness d, and the light wavelength. In these structures, the apparent Faraday rotation consists of two parts. One oscillates as a function of the M-O layer thickness and the other is proportional to the layer thickness. The oscillation period and the amplitude are determined by the optical constants of the M-O layers. For the air/M-O/reflector configuration, the Kerr rotation φk oscillates as a function of the M-O layer thickness and approaches a constant as the thickness d→∞. If the M-O layers are semitransparent and weakly magnetic, the apparent Kerr rotation can be expressed as φk=e2φF′. For ultrathin metallic magnetic bilayered films the Kerr rotation is proportional to the M-O layer thickness and the enhancement factor is a function of the optical constants of the M-O layer and NM reflector. The magneto-optics of a Co spinel ferrite film, Co/Cu, Fe-Ni/Cu, and Co/Si structures have been studied experimentally.In this article the magneto-optics of magneto-optical (M-O) layered structures have been studied theoretically and experimentally. For the air/M-O/air configuration, an analytic expression between the apparent complex Faraday rotation and the eigenvalue φF=e1φF′ can be obtained, when the M-O layers are semitransparent and weakly magnetic. The interference factor e1 is a function of the optical constants and the M-O layer thickness d, and the light wavelength. In these structures, the apparent Faraday rotation consists of two parts. One oscillates as a function of the M-O layer thickness and the other is proportional to the layer thickness. The oscillation period and the amplitude are determined by the optical constants of the M-O layers. For the air/M-O/reflector configuration, the Kerr rotation φk oscillates as a function of the M-O layer thickness and approaches a constant as the thickness d→∞. If the M-O layers are semitransparent and weakly magnetic, the apparent Kerr rotation can be expressed as φ...

The magneto-optical properties of Co–Ag granular films

Abstract The magneto-optical properties of Co x Ag 100− x granular films annealed at 100, 250, 400, 500°C, respectively, were carefully studied. Both the optical and magneto-optical constants were measured in the experiment. It was found the Kerr rotation and ellipticity increased with increasing content of Co. For the samples Co 2 Ag 98 , the Kerr effect is enhanced dramatically with the resonant peaks appearing in the 3.7–4.1-eV photon energy range after annealing. In terms of the optical constant and the magneto-optical quantity of e xy , the line shape of the Kerr spectra origin is analyzed. The peaks are attributed to the plasma oscillation correlated to the onset of the interband transition that is related to the band structure of the granular films with increasing granular size after annealing.

The medium-related optical constants of noble metals observed by ellipsometric study

The optical constants used in metallic multilayer structures may differ from those measured in air using a two-phase model and thus will affect the design performance of an optical device. To understand the effect better, we used Dove prisms with different refractive indices as the substrates. The spectroscopic ellipsometry method was used to measure directly the optical constants of Ag and Au films which were thermally or electron-beam evaporated on the bottom of the prisms. In this configuration, the optical constants of the films can be measured at the metal-air and metal-substrate interfaces. Upon data reduction, we found that the optical constants of a given film measured at the metal-substrate interface do change with the refractive index of the substrate and differ from those measured at the metal-air interface in both of the Drude and interband transition regions. These results agree with those obtained by other authors in a liquid-contacting situation, and need to be studied in great detail in the future.

Study of magneto-optical properties of Ni : SiO2 granular films

A series of NixSiO2(1−x) granular films was prepared by ion sputtering, and some of them were annealed. Both the complex dielectric function and magneto-optical polar Kerr spectra of the samples were measured in the 1.5–4.5 eV photon energy range at room temperature. There are broad peaks in the 2.5–3.5 and 3.2–4.5 eV range in the Kerr rotation and ellipticity spectra, respectively. The Kerr intensities increase with increasing Ni composition. For sample x=0.65, the Kerr peaks are redshifted, with reduced intensities after annealing. Both the off-diagonal terms of the dielectric tensor and the optical constants are attributed to enhancement of the Kerr effect in a particular spectral range for the metal–insulator granular films.

Temperature dependence of magneto-optical properties of Zn1-xMnxSe

This paper reports the temperature dependence of the magneto-optical properties of Zn1-xMnxSe samples prepared by molecular beam epitaxy method. In the magneto- optical spectra, there exist several Faraday rotation peaks. The peaks located at approximately 2.18, approximately 2.36 and 2.45 - 2.57 eV are attributed to Mn2+ d yields d* transitions. The peak located at approximately 2.7 eV is attributed to the interband transitions and higher order Mn2+ d yields d* transitions, which are blue-shifted with decreasing temperature. The positions of the rotation peaks induced by Mn2+ d yields d* transitions show weak temperature dependence.

Giant magnetoresistance effect in granular-type Co-Ag/Ag multilayers

For the granular type of Co-Ag (1.8 nm)/Ag multilayers with the Co contents of 22, 45, and 65 at%, the magneto-resistance ratio ((Delta) R/R) has a maximum found with respect to the AG spacer layer thickness. It is found that with increasing Co content the (Delta) R/R peak shifts towards thicker AG layers. For the Co-Ag/Ag multilayers with low Co contents, (Delta) R/R increases monotonically with increasing magnetic layer thickness, but has a maximum near the magnetic layer thickness of 2.2 nm for the sample having a higher Co content. The peak is thought as a result of the antiferromagnetic (AFM) coupling between the nearest Co clusters in neighboring magnetic layers. In the high field region, the magnetization and the square root of (Delta) R/R vary as a linear function of the reciprocal applied field for all multilayers. In the low field range, they are proportional to the applied field for samples with thin magnetic layers.

The Magnetic Coupling, Optical and Magneto-Optical Properties of Oscillation Observed in Sputtered Co–Al/Cu Multilayers

We have studied the optical and magneto-Optical properties, and the behavior of interlayer coupling and magnetoresistance in sputtered [Co 90 Al 10 (1.6 nm)/Cu] 30 multilayers. It is found that for Co-Al/Cu multilayers. the magnetoresistance ratio ΔR/R, the in-plane saturation field H s and coercive force H c oscillate with a period of about 0.9 nm, as a function of the Cu layer thickness. It is significant to find that the magneto-Optical polar Kerr rotation θ K , and particularly the effective dielectric constant e oscillate in a period of about 0.9 nm. This result can be attributed to the oscillations of the optical constants in Cu spacer layers. induced by the oscillatory interlayer coupling or quantum well effect. Numerical calculations show that the oscillations of the effective optical constants play an important role in the magneto-Optical Kerr effect oscillations.