Wenbin Xia

Optical and magneto-optical anisotropies in large-area two-dimensional Co antidots film.

In this work, we investigate the plasmon-induced optical and magneto-optical anisotropies in the large-area square-ordered Co antidots film. It shows that both the outline of reflectivity spectrum and Kerr spectrum are significantly modified by surface plasmon polarition (SPP) resonances. Moreover, the magnitude of Kerr angle reaches to about 10 minutes at the azimuthal angle 45°, which is over 3 times of that of pure Co film. These phenomena are attributed to the SPP resonances with different diffraction orders of reciprocal lattice vectors.

Temperature dependence of the magnetostriction in polycrystalline PrFe1.9 and TbFe2 alloys: Experiment and theory

A remarkable magnetostriction λ111 as large as 6700 ppm was found at 70 K in PrFe1.9 alloy. This value is even larger than the theoretical maximum of 5600 ppm estimated by the Stevens equivalent operator method. The temperature dependence of λ111 for PrFe1.9 and TbFe2 alloys follows well with the single-ion theory rule, which yields giant estimated λ111 values of about 8000 and 4200 ppm for PrFe1.9 and TbFe2 alloys, respectively, at 0 K. The easy magnetization direction of PrFe1.9 changes from [111] to [100] as temperature decreases, which leads to the abnormal decrease of the magnetostriction λ. The rare earth sublattice moment increases sharply in PrFe1.9 alloy with decreasing temperature, resulting in the remarkably largest estimated value of λ111 at 0 K according to the single-ion theory.

Giant magneto-optical Kerr effect in HfO2/Co/HfO2/Al/silicon structure

An extraordinary enhancement of magneto-optical Kerr effect was demonstrated in HfO2/Co/HfO2/Al/substrate composite structure by experimental measurements as well as theoretical calculations. Giant polar Kerr rotation was observed within a broad spectral region, and especially a peak of −7.92° was found at wavelength of 496 nm, which is nearly forty times as large as that of a single Co film. In addition, a Kerr rotation reversal was also observed in short wavelength region in the longitudinal geometry. We proposed that the multiple reflections and optical interference in the optical cavities lead to the enormous enhancement and modulation of the Kerr rotation.

The evolution of magnetic domain structure with magnetic history in amorphous film with perpendicular anisotropy

Amorphous rare-earth-Fe-B (RE-Fe-B) films were deposited on Si substrates at 300 °C by dc magnetron sputtering. The evolution of their magnetic domain structures with magnetic history was observed by magnetic force microscopy. It was found that the remanent domain configuration can be gradually transformed from stripes to bubbles after applying different magnetic fields along the out-of-plane direction, which indicates that the film has a perpendicular magnetic anisotropy. In addition, an in situ investigation on the evolution of domain structure under an in-plane field was carried out using a homemade sample holder. The results showed that the domain structure depends on both the applied field and the magnetic history. The present work provides a feasible approach for manipulating magnetic domains in amorphous RE-Fe-B film by employing a magnetic field.

Giant low-temperature magnetostriction and spin-reorientation of polycrystalline alloy PrFe1.9

A remarkably giant intrinsic magnetostriction λ111 as high as 6700 ppm was found at 70 K in PrFe1.9 compound, which is much larger than the value of 5600 ppm predicted by single-ion theory. Change of the easy magnetization direction from [111] to [100] with decreasing temperature occurs between 30 and 70 K, which was verified by step-scanned {440} and {222} X-ray diffraction reflections. It was further demonstrated that this compound has a rhombohedral symmetry between 70 and 300 K, and a tetragonal symmetry between 15 and 30 K. Therefore, the magnetostrictive anomaly at low temperature may be interpreted by the spin reorientation transition of the compound. PrFe1.9 with high magnetostriction is a good candidate material for magnetostriction applications at low temperature.

Magneto-optical properties of one-dimensional orderly nanocorrugation made from magnetic quadrilayer films

Magneto-optical (MO) Kerr effect and optical reflectance are investigated in the visible light region for one-dimensional orderly nanocorrugation of magnetic quadrilayer films. We find that the MO enhancement originates from the combined action between cavity effect and surface plasmon resonance. The coupling between surface plasmon polaritions and localized surface plasmons cannot only enhance the magnitude of Kerr angle, but also alter the sign of Kerr rotation. In addition, the MO properties on the nanocomposite films can be tuned by the thickness of the intermediate HfO2 layer due to the cavity effect in multilayer.

Enhanced magnetic performance of metal-organic nanowire arrays by FeCo/polypyrrole co-electrodeposition

FeCo/polypyrrole (PPy) composite nanowire array, which shows enhanced magnetic remanence and coercivity along the nanowires, was fabricated by AC electrodeposition using anodic aluminum oxide templates. High resolution transmission electron microscopy shows that PPy grows on the surface of FeCo nanowires forming a coaxial nanowire structure, with a coating layer of about 4 nm. It suggests that the decreased dipolar interaction due to the reduced nanowire diameters is responsible for the enhancement of magnetic performance. The possible mechanism of this coating may be that PPy is inclined to nucleate along the pore wall of the templates.

Thermally assisted manipulation of magnetic domain structures in amorphous rare-earth-Fe-B film

The temperature dependence of domain evolution in amorphous rare-earth-Fe-B film is investigated via magnetic force microscopy as well as magnetization measurements. Within an external 1.0 kOe magnetic field perpendicular to the film, the domains evolve from stripes to bubbles as the temperature increases. Both of the domain wall motion and domain nucleation processes are found to be independent of the film defects. It leads to the formation of nearly perfect bubble domains with their sizes exhibiting a Gaussian distribution. If the external field is removed, the magnetic field generated by the scanning tip has to be taken into consideration. It is found that the tip field, although weak and localized, can modify the local domain structure within the scan area at 373 K. To explain the experimental results, we propose that the domain structure is usually stuck in one of the metastable states separated by energy barriers at a given temperature. The switching between different states is commonly governed by ...