Z. Z. Zhang

Compositional control of FexPt(1−x) nanowires by electrodeposition

FexPt(1−x) nanowire arrays embedded in porous alumina membranes with controlled diameters and high aspect ratios were fabricated by the pulse electrodeposition method in a novel bath with a simple composition. The composition of FexPt(1−x) nanowires can be highly controlled by the negative deposition voltage and the pulse duration. A growth mode of alternating Fe and Pt composition within wires is observed for electrodeposition in different periods of pulse time. The space separation between the iron-rich layer and the platinum-rich layer contributes to the relatively low coercivity of FexPt(1−x) nanowire arrays with an atomic ratio of 1:1.

Deposition of YBa2Cu3O7−x films on Si with conductive indium oxide as a buffer layer

Abstract The superconducting YBa 2 Cu 3 O 7− x (YBCO) thin films have been grown in in situ on Si with a conductive indium oxide (In 2 O 3 ) buffer layer. The buffer layer, sputtered by the reactive dc magnetron method, was used to minimize interdiffusion between Si and the superconductor. The as-deposited thin films, without post high-temperature annealing, has a T c onset at 98 K with zero resistance at 81 K, X-ray diffraction data indicate that the films have a preferential c -axis oriented structure. Auger electron spectroscopy (AES) and Rutherford back scattering (RBS) have been employed to study the diffusion and structure variation near interfaces.

The role of the silver intermediate layer in the YBa2Cu3O7−x/Ag/ In2O3/Si system

Abstract Superconducting YBa 2 Cu 3 O 7− x (YBCO) thin films were deposited on Si(111) substrates with a conductive intermediate layer of Ag In 2 O 3 . In 2 O 3 was prepared by the d.c. magnetron method and a silver thin film was evaporated on the In 2 O 3 /Si(111). The YBCO thin films were deposited by d.c. magnetron sputtering. The conductive In 2 O 3 thin film was used to minimize the interdiffusion between silicon and the YBCO superconducting material. The silver thin film improves the zero-resistance temperature, transition temperature width, and the critical current density of the superconducting YBCO film in the YBCO/In 2 O 3 /Si system. Films of YBCO on the Ag/In 2 O 3 /Si substrate have zero resistance at 85 K and a critical current density of 2.0 x 10 3 A cm −2 at 77 K. The XRD spectrum indicates that the superconducting thin films have a preferential c axis oriented structure. Auger electron spectroscopy depth profiling was used to analyse the interfaces.

Depositing In2O3 films as conductive buffer layers for high temperature YBa2Cu3O7−x superconducting thin films on silicon

Abstract By depositing a conductive buffer layer of In 2 O 3 , we have been able to prepare superconducting YBa 2 Cu 3 O 7− x on silicon by d.c. magnetron sputtering. The buffer layer sputtered by the reactive d.c. magnetron method was used to minimize the interdiffusion between silicon and the superconductor. The typical as-deposited superconducting thin film, without subsequent high temperature annealing, has a T c onset at 96 K with zero resistance at 81 K. X-ray diffraction data indicate that the films have a preferential c axis oriented structure. Depth profiling by Auger electron spectroscopy has been employed to study the diffusion and structural variation near the interfaces.

Magnetization reversal of L10 FePt/Co/Fe trilayers

With a thin Co layer inserted into the L10-FePt(3 nm)/Fe(2 nm) ECC structure, a large reduction of coercivity is observed in such a graded trilayer, with a minimum value of 1.45 kOe when the Co thickness is 2 nm, similar to that of FePt(3 nm)/Fe(4 nm). The magnetization reversal in both FePt/Fe and FePt/Co/Fe structures is carefully studied by the vector vibrating sample magnetometer. The nucleation, wall compression, and irreversible magnetization rotation are discussed.

The structure and magnetic properties of FePt based perpendicular exchange coupled composite films

Two series of FePt/[Co/Pt]N (FPCP-N) and FePt/[Co/Ni]N (FPCN-N) exchange coupled composite (ECC) films were prepared and studied. Well isolated island-like grains with an average grain size of about 20nm are obtained. Both FePt hard layer and Co based soft multilayer are of perpendicular anisotropy. Large reduction of the switching field is observed when the Co based multilayer is deposited on the top of FePt films. When the thickness of Co based multilayers increase, thermal stability of the composites decreases slightly in both two series. Therefore, low switching field and high thermal stability are both obtained in these perpendicular ECC films.

Formation of (001) Texture in Fe-O Underlayered

L10 FePt thin films were deposited on an Fe-O underlayer prepared by RF bias sputtering in an oxygen atmosphere for different oxidization time. Very good (001) texture and perfect perpendicular magnetization were obtained in the FePt film on 1-nm-thick Fe-O underlayer after high temperature annealing. The (001) texture evolution was accompanied by fcc-to-fct phase transformation, and both were driven by a recrystallization process. The Fe-O underlayer not only acts as a template, but also provides a stress to help the atom migration during annealing.

L1_{0}

TbFeCo is an important MO media material and even a candidate for hybrid recording. Our experimental results show that two magnetic phases can co-exist in TbFeCo films with orthogonal easy axes, which are along the film plane or out-of-plane. Suggested by the hystersis curves measured by the extraordinary Hall effect (EHE) and vibrated sample magnetometer (VSM), there is a transition region between domains with different easy axes of magnetization. The exchange coupling in between acts as a biased field, which may migrate the magnetic switching field for each loop.