Ya‐Dong Wang

MAGNETOOPTICAL KERR EFFECT IN FE-SIO2 GRANULAR FILMS

Polar Kerr rotation spectra of Fe‐SiO2 granular films were measured at room temperature in the wavelength region between 400 nm and 850 nm. A maximum Kerr rotation angle (θk) of 18 min was obtained when a magnetic field of 10 kOe was applied perpendicular to the film plane. We have measured θk as a function of Fe volume fraction (fv) of the films. It was found that θk increases with increasing fv and peaks at fv≊0.4. We also found that θk decreases as the Fe particle size increases. Our results indicate that the density of Fe particles and the interfaces between Fe particles and SiO2 matrix may play an important role in the Kerr rotation of granular films.

Oscillations of interlayer coupling and magneto‐optics in sputtered Co–Al/Cu multilayers

We have prepared [Co90Al10/Cu]30 multilayers by ion beam sputtering and studied the behavior of interlayer coupling, magnetoresistance, and the magneto‐optical Kerr effect. For Co–Al/Cu multilayers, the in‐plane saturation field, coercive force HC and magnetoresistance ratio ΔR/R have been observed to oscillate with a period of about 0.9 nm, as a function of Cu spacer layer thickness. Furthermore, polar Kerr rotation θk in visible wavelength range also oscillates with the same period. The magneto‐optical activities may be attributed to changes in the optical constants with the magnetic state.

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...

STUDIES OF OPTICAL AND ELECTRONIC PROPERTIES IN CO/AG MULTILAYERS

We have studied the electronic structure and optical properties, in the photon energy range of 3.0–4.5 eV, of sputtered Co/Ag multilayers with a scanning ellipsometer and Kerr spectrometer. It is found for the multilayer series Co(1.2 nm)/Ag and Co/Ag with dCo/dAg=2/3 that the screened plasma frequency ωp* of the multilayers and the interband transition frequency ω0 for L3→L2′ (d band to Fermi surface near the L point) in the Ag layers shift towards lower energy with increasing Ag layer thickness or modulation wavelength. For the second series of samples, the Kerr rotation peak also shifts towards lower energy with increasing modulation wavelength. For a third series of Co/Ag(1.3 nm) multilayers, only ω0 moves towards lower energy with an increasing Co layer thickness. The variation of ω0 is not easily explained in terms of internal strains and changes of the lattice constants in the Ag layers. Further theoretical analysis is needed.

Study of apparent Faraday rotation of an optically anisotropic system

We present a formula which can be used to analyze the anisotropic and apparent Faraday effect occurring in a material having an optically anisotropic property. By using the formula the real Faraday parameter can be obtained. For example, we have used the formula to study the anisotropic Faraday effect of a single‐crystal Cd0.55Mn0.45Te measured with the spectroscopic ellipsometer and rotating‐analyzer‐type Kerr apparatus. The calculated data were in good agreement with the experimental results.

Ferromagnetic resonance studies of noble metals based sandwiches

In this paper we have prepared Fe/Cu, Ag, Au/Fe sandwiches by ion beam sputtering and studied the interlayer coupling behavior by ferromagnetic resonance technique. In these sandwiches the Fe and noble metal layers are polycrystalline in the textures of (110) and (111), respectively. It is found that the in‐plane resonance field and the linewidth oscillate as a function of nonmagnetic layer thickness in a period of about 1.0 nm for Fe/Cu, Au/Fe structures, and 1.4 nm for Fe/Ag/Fe system. It is suggested that the interlayer coupling strength between the ferromagnetic layers oscillates in the same period with the resonance field. An in‐plane anisotropy was found in Fe/Ag/Fe system.

CHARACTERISTICS OF HIGH-ENERGY N+-IMPLANTED DAMAGE IN GASB

Abstract Characteristics of 2 MeV N+-implanted damage in GaSb samples with doses from 1 × 1013 cm−2 to 1 × 1015 cm−2 were studied by use of spectroscopic ellipsometry, Rutherford backscattering spectrometry in combination with the channeling technique, and scanning electron microscopy methods. When doses are greater than 3 × 1014 cm−2, the implanted layer becomes amorphous. But no swelling was observed on the implanted sample surfaces, as predicted by R. Callec. By rapid thermal annealing at 600°C for 25 s, a good recovery of the implanted layers has been achieved.

Magnetic and magneto-optic properties in CoNb/Pd and FeSi/Cr multilayers

Abstract In this paper the magnetic and magneto-optical properties of CoNb Pd and FeSi Cr multilayers are studied. For CoNb/Pd(56 A) multilayers, with decreasing magnetic layer thickness the saturation magnetization M s is the same for polar Kerr rotation θ k and ellipticity ϵ k decrease. For CoNb(15 A)/Pd FeSi(19 A)/Cr multilayers with thin non-magnetic layers M s and θ k oscillate with non-magnetic layer thickness. The oscillation period of M s is the same for these two series of samples. With non-magnetic layer thickness further increasing, M s and θ k both approach constants.

Oscillation effects in the magnetic and optical properties of Co-Al/Cu multilayers

Abstract A series of [Co90Al10(1.6 nm)/Cu]30 multilayer samples were made to study the oscillatory interlayer coupling using a vibrating sample magnetometer (VSM), giant magnetoresistance (GMR), surface magneto-optical Kerr effect (SMOKE), magneto-optical Kerr effect (MOKE) and spectrscopic ellipsometry methods. The measured value of ΔR/R, in-plane saturation field (Hs), MOKE and effective dielectric constant ɛ were found to have an oscillation period of 0.9 nm as a function of the Cu-layer thickness. The oscillations observed in those experiments arises from the same origin related to the interlayer coupling or quantum-well effect.

The magneto‐optical and optical properties of ultrathin Fe films in the short‐wavelength range

The magneto‐optical and optical properties of ultrathin Fe films sandwiched between Au layers were studied. A pronounced Kerr rotation peak is observed respectively in the photon energy range of 3.6–3.8 eV when the Fe layer is thinner than 1.5 nm, and in the range of 3.4–3.5 eV for thicker Fe layers. In simple calculations, the Kerr rotation peak is demonstrated to originate from the variation of the off‐diagonal element in dielectric tensor of the Fe layers. The relative peak height Δθk, the normalized Kerr rotation θkn, and the effective optical constants at the photon energy of 3.5 eV are found to oscillate as a function of dFe.