Y.Z. Miao

Anisotropy and Faraday effect in Co spinel ferrite films

Crystalline Co spinel ferrite films were prepared by rf sputtering on glass substrates without buffer layer and annealed at temperatures from 400 to 600 °C for 2 h in air. (100) texture was obtained in these films. The anisotropy constant, magnetic hysteresis loops, and magneto‐optical Faraday spectra of the films were measured. The texture became poor when the films were annealed below 500 °C, but the perpendicular anisotropy constant Ku, squareness ratio R=(Mr/Ms)⊥/(Mr/Ms)∥ increased and showed peak values of 2.2×105 ergs/cm3 and 0.94, respectively, at an annealing temperature Ta=500 °C. For the film annealed at 600 °C (higher than the Curie temperature, 520 °C, of Co spinel ferrite), the texture recovered, but Ku and R dropped. The Faraday rotation spectra of Co spinel ferrite films showed a broad peak centered around 720 nm. The peak value increased monotonically with increasing annealing temperature. These results may be related to the Co ion‐induced anisotropy and Co ion distribution in tetrahedral ...

Magneto-optics in layered and multilayered films

Abstract The magneto-optical Kerr rotation in various bilayer, trilayer and multilayer films are studied experimentally and theoretically. In bilayers and trilayers the enhancement of Kerr rotation by a factor of two to five based on the reduction of effective optical constants has been achieved with a reasonable reflectivity. The enhancement can be realized in the whole wavelength region, from near IR to near UV. In Fe/Pd and FeSi/Cu multilayer films an additional magneto-optical activity related to the exchange polarization of Pd and Cu layers is observed. Multilayer films with broad opportunities for reducing effective optical constants and creating additional magneto-optical activities are demonstrated to be a promising area for finding new magneto-optical materials.

Spin polarization and additional magneto-optical activity of nonmagnetic layers in Fe/Ag CMF☆

Abstract The experimental magneto-optical Kerr rotation spectra of Fe/Ag compositionally modulated films reported by Katayama et al. are studied theoretically. It is found that the free electrons of Ag are spin polarized. The magnitude of the polarization is about 1% with a direction opposite to that of Fe. The polarized Ag also gives rise to an additional magneto-optical activity as in Pt and Pd.

Evidence of magnetization of Ag in Fe/Ag compositionally modulated films by MOKE spectra

Abstract Theoretical and experimental studies of θ K spectra demonstrated that the conduction electrons of Ag in Fe/Ag CMF are spin polarized and give an additional MO activity. In FeCo/Cu/FeCo sandwiches, an oscillation of θ K with changing thickness of Cu was observed, which may indicate an oscillatory spin polarization of Cu layers.

Interlayer coupling and spin polarization of the nonmagnetic layers in Fe/Cu and Fe/Ag CMFs

Compositionally modulated films (CMFs) of Fe/Cu and Fe/Ag, made by RF sputtering, were investigated with ferromagnetic resonance (FMR), nuclear magnetic resonance (NMR), and magneto‐optical (MO) spectroscopy. Evidence of spin polarization of the nonmagnetic layers, related to the interlayer coupling, was obtained. Direct evidence of the penetration of an exchange field and the spin polarization of the conduction electrons in the nonmagnetic Cu layers was obtained in Fe/Cu CMFs by NMR. Spin‐wave resonances were observed in Fe/Cu CMFs in FMR experiments, and the spin wave was found to be sustained by both the Fe and Cu sublayers. The MO spectra of Fe/Ag CMFs indicated that the conduction electrons of Ag are spin polarized and give an additional MO activity.

Complex magneto‐optical Kerr rotation of Fe,FeCo/Cu multilayer films

The complex magneto‐optical Kerr rotation spectra of Fe/Cu and FeCo/Cu bilayers and compositionally modulated films (CMF) were studied experimentally and theoretically. In the bilayers, an enhancement of Kerr ellipticity ek by a factor of 5 was observed at long wavelength side, while the Kerr rotation θk can only be enhanced by a factor of 2 around the plasma edge of Cu. In the CMFs, ek was enhanced by 60% but no θk enhancement was observed. Theoretical analyses showed that both the magnitude of effective exye and the magnitude and signs of effective Ae and Be are important for magneto‐optical enhancement.

Thickness and substrate dependence of the magneto‐optical Kerr effect of thin magnetic films

Different thickness dependencies of the magneto‐optical Kerr effect of the magnetic (Co, Ni, and Fe)/nonmagnetic (air, glass, Cu, and W) bilayer structures were studied experimentally and theoretically, showing the complicated influence of the dielectric constants of the underlying substrate.

The magneto‐optical Kerr effect of bilayers Fe/Au‐Cu and Fe/Ag‐Au

Bilayers Fe/Au‐Cu and Fe/Ag‐Au made by vacuum evaporation were studied. The magneto‐optical polar Kerr rotation and reflectivityspectra were measured in the region from 400 to 700 nm. In the magneto‐optical Kerr rotation spectra of bilayers Fe/Au‐Cu and Fe/Ag‐Au with the thickness of Fe layer less than the light penetration depth, there is a broad enhancement of the magneto‐optical polar Kerr rotation with a Kerr peak near the plasma edge in the reflectivityspectra of Au‐Cu and Ag‐Au alloys. The peak shifts toward the long wavelength side with increasing Cu and Au content in Au‐Cu and Ag‐Au alloys, respectively. Our results show that the composition of the reflector in our bilayer structures can shift the wavelength range of the magneto‐optical Kerr rotation enhancement. Interpretation and discussions are given.

Magneto-optical Kerr effect of NdFe films and NdFe/Cu bilayers☆

Abstract Magneto-optical Kerr rotation (MOKR) spectra of single films Nd-Fe and bilayers NdFe/Cu, NdFe/Al made on glass substrates by vacuum evaporation were measured. It is found that there is a broad enhancement on MOKR spectra for bilayers NdFe/Cu and NdFe/Al and a Kerr peak for NdFe/Cu bilayers.

Spin polarization of nonmagnetic layers in multilayers

Abstract Magnetic measurements, ferromagnetic resonance, magneto-optical Kerr rotation and nuclear magnetic resonance have been used to study the spin polarization of nonmagnetic layers of Pd, Cu, Ag and Al in multilayers and sandwiches containing Fe, Co, FeCo and CoCr. The existence of the spin polarization of Pd, Cu, Ag and Al was demonstrated directly or indirectly.