K.D. Aylesworth

Growth and control of the microstructure and magnetic properties of sputtered Nd2Fe14B films and multilayers

Abstract The magnetic and structural properties of sputtered films of Nd17 (Fe0.9Co0.1)76B7 (NFB) and multilayers of NFB with Ag and Fe have been examined. The structure of each film was determined by small- and large-angle X-ray diffraction, and the magnetic properties were measured in a room-temperature vibrating-sample magnetometer (VSM) with a maximum field of 17.1 kOe and cryogenic VSM with a maximum field of 80 kOe. The amount and orientation of the 2 : 14 : 1 phase in the samples were found to depend strongly upon the substrate material and degree of target oxidation. The primary contaminant in most of the samples studied is a fcc phase with a = 5.110 A , tentatively identified as NdO. The direction of the easy axis (axes) of the films can be correlated with the average c-axis orientation of the 2 : 14 : 1 grains, which in turn can be controlled by the application of an external magnetic field during sample annealing and crystallization. Nearly single-phase films can be produced with a maximum room-temperature coercivity of about 6 kOe and a magnetization of about 100 emu/g. Samples containing significant amounts of NdO have coercivities up to 10 kOe, but the magnetization then drops to about 40 emu/g. The magnetic properties of the multilayers also depend stongly upon the individual layer thicknesses.

Magnetic and structural properties of Nd2Fe14B permanent‐magnet films and multilayers with Fe and Ag

Etude des effets des conditions de pulverisation sur la structure et les proprietes magnetiques de couches et de multicouches de Nd 2 (Fe 0,9 Co 0,1 ) 14 B

Magnetic properties, anisotropy, and microstructure of sputtered rare‐earth iron multilayers

A study of compositionally modulated magnetic films of the form Fe/RE, particularly for RE=Nd and Dy, has been performed by vibrating sample magnetometry, ac susceptibility and x‐ray diffraction. The relationship between the magnetic properties and the layer thickness was studied systematically for X‐A Fe/Y‐A Dy, as the layer thicknesses X and Y were varied from 1.8 to 20 A. The ranges of layer thicknesses required for perpendicular anisotropy were determined. The interface and volume anisotropy energies were estimated for X‐A Fe/Y‐A Nd and the differences in the magnetic properties between X‐A Fe/7‐A Dy and X‐A Fe/7‐A Nd are discussed.

The structural and magnetic properties of films of Pr2Fe14B and Nd2Fe14B cosputtered with Ta

Abstract The results of structural and magnetic measurements on films, produced by serially depositing R2Fe14B (R = Nd, Pr) and Ta, are reported. The materials were deposited 10–200 A at a time onto 500–700°C Ta substrates. The structures of the resulting films were examined by large- and small-angle X-ray diffraction. The magnetic properties were studied at room temperature in a Vibrating Sample Magnetometer (VSM) with a maximum field of 17.1 kOe, and at cryogenic temperatures in a VSM with a maximum field of 80 kOe. The structural and magnetic properties depend upon the nominal thickness of the Ta, even though interlayer diffusion appears to be significant for Ta thickness less than about 30 A. The trends in the coercivities can be qualitatively explained by assuming a nucleation mechanism for magnetization reversal and correlating the coercivity with the degree of c-axis alignment in the 2:14:1 phase.

Highly oriented Tl2Ba2Ca2Cu3O10 thin films by pulsed laser evaporation

We have fabricated superconducting thin films on MgO(100) substrates with nearly pure Tl2Ba2Ca2Cu3O10 (2:2:2:3) phase using pulsed laser evaporation and post‐annealing. The films had c axes perpendicular to the substrates. Superconducting films with onset temperatures of 125 K and zero resistance at 110 K were obtained. X‐ray microprobe fluorescence measurements indicate that a typical composition of films is Tl0.66Ba1.77Ca1.46Cu3Ox, which is low in Tl compared to that expected for the 2:2:2:3 phase. A typical grain size is greater than 10 μm as revealed by scanning electron microscopy.

Magnetic and structural properties of high‐coercivity Pr2Fe14B: Pr cosputtered films

The results of structural and magnetic measurements on a series of films produced by cosputtering Pr21Fe72B7 and Pr are reported. The materials were deposited serially, 10–200 A at a time, onto 700 °C Ta substrates attached to a computer‐controlled stepping motor. The structure of the resulting films was examined by large‐ and small‐angle x‐ray diffraction, scanning electron microscopy, and by microprobe analysis. Magnetic measurements were made at temperatures from 4.2 to 300 K, in fields up to 80 kOe in a vibrating sample magnetometer. The films appear to consist of 1‐μm grains of Pr2Fe14B with their c axes oriented perpendicular to the film plane, surrounded by a Pr‐rich phase. The maximum room‐temperature coercivity discovered so far is almost 20 kOe, which is close to the values reported for bulk Pr2Fe14B magnets.

Magnetic properties of rapidly quenched and annealed Fe10RTi and related alloys

Magnetic measurements are reported for iron‐rich ternary alloys with the following compositions: Fe10NdxDy1−xTi (0≤x≤1), Fe10SmM (M=Ti, V, and Mo), and Fe10RV (R=Y, Gd, and Dy). The samples were prepared by splat cooling or melt spinning and selected samples were heat treated. The results of x‐ray diffraction, electron microscopy, and thermomagnetic measurements on the Fe10NdxDy1−xTi series are presented and indicate that the rapidly quenched alloys are nearly single phase and become multiphase upon heating. Magnetic measurements on the other two series show that the substitution of V for Ti increases the saturation magnetization.

Thermal and structural stability of cosputtered amorphous TaxCu1−x alloy thin films on GaAs

The thermal and chemical stabilities of amorphous‐metal diffusion barrier films are of importance in high‐temperature semiconductor device applications. The reaction characteristics of the barrier constituents with the surrounding elements as well as the crystallization temperature determine the thermal stability of an amorphous‐alloy diffusion barrier. We report that suitable thin films of Ta‐Cu have been prepared over a wide range of compositions, by cosputter deposition onto GaAs and fused‐quartz substrates. The amorphous nature and crystallization behavior of the films have been monitored by x‐ray diffraction and van der Pauw resistivity measurements. Films were found to be amorphous over the range of 55–95 at. % Ta. In addition, Auger electron spectroscopy surveys and depth profiles were used to investigate the various interdiffusion reactions between the amorphous diffusion barrier, polycrystalline Au overlayers, and GaAs substrates. Barriers of Ta93Cu7 are remarkably effective in preventing Au in‐d...

Microstructure studies in Nd2(Fe0.9Co0.1)14B thin films

Abstract Large coercive fields (above 10 kOe) have been produced in thin sputtered films of Nd(FeCo)B. The films were either deposited at room temperature and heat treated or deposited onto high-temperature substrates (to about 730 °C). Transmission electron microscopy was used to study the microstructure and magnetic domain structure of the films. Correlations were observed between sputtering and growth parameters, microstructure and magnetic properties.

Highly oriented Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ thin films by pulsed laser evaporation

We have fabricated superconducting thin films on MgO(100) substrates with nearly pure Tl2Ba2Ca2Cu3O10 (2:2:2:3) phase using pulsed laser evaporation and post‐annealing. The films had c axes perpendicular to the substrates. Superconducting films with onset temperatures of 125 K and zero resistance at 110 K were obtained. X‐ray microprobe fluorescence measurements indicate that a typical composition of films is Tl0.66Ba1.77Ca1.46Cu3Ox, which is low in Tl compared to that expected for the 2:2:2:3 phase. A typical grain size is greater than 10 μm as revealed by scanning electron microscopy.