Dc Triode Sputtering Research Articles

Spin Wave Theory and Ab Initio Calculations in Co/C Multilayers: Interfacial Effects

Co/C multilayers were prepared using DC triode sputtering with different Co thicknesses (tCo), and their magnetic properties were investigated using a vibrating sample magnetometer. It is found that the magnetization of Co layers decreases with decreasing tCo, at thicknesses below 6 nm, which can be understood by the presence of a magnetically dead layer, due to intermixing between Co and C layers, i.e., the alloy formation around the former interface. A model based on the spin-wave theory was utilized to explain the change of the magnetization as function of temperature, and estimate the coupling exchange interaction. Ab initio calculations were utilized to explain the decrease of the magnetic moment within the interfacial layer (Co1-xCx). In addition, the influence of pressure on the magnetic properties of the Co1-xCx layer was studied as well.

Magnetic Studies in Sputtered Ni/Ti Multilayers

Magnetic properties of Ni/Ti multilayers, prepared by the DC triode sputtering method, have been studied by magnetic measurements. Both metal layers are crystalline with a (111) fiber structure when they are thicker than 20 A. The magnetization decreases with a decrease in Ni layer thickness tNi and the analysis of the results at 5 K indicates the presence of a dead Ni layer about 13 A thick. The effective anisotropy Keff of Ni/Ti multilayers is obtained using a torque magnetometer. Spin-wave theory has been used to explain the temperature dependence of the magnetization. Approximate values for bulk exchange interaction Jb, surface exchange interaction JS and interlayer coupling strength JI for various Ni layer thicknesses have been obtained.

Reactively sputtered Ni, Ni(N) and Ni 3N films: Structural, electrical and magnetic properties

Nickel thin films were deposited on glass substrates at different N 2 gas contents using a dc triode sputtering deposition system. Triode configuration was used to deposit nanostructured thin films with preferred orientation at lower gas pressure and at lower substrate temperature compared to the dc diode sputtering system. A gradual evolution in the composition of the films from Ni, Ni(N), to Ni 3N was found by X-ray diffraction analysis. The preferred growth orientation of the nanostructured Ni films changed from (1 1 1) to (1 0 0) for 9% N 2 at 100 °C. Ni 3N films were formed at 23% N 2 with a particle size of about 65 nm, while for 0% and 9% of nitrogen, the particles sizes were 60 nm, and 37 nm, respectively, as obtained by atomic force microscopy. Magnetic force microscopy imaging showed that the local magnetic structure changed from disordered stripe domains of about 200 nm for Ni and Ni(N) to a structure without a magnetic contrast, indicating the paramagnetic state of this material, which confirmed the structural transformation from Ni to Ni 3N.

DC triode sputtering deposition and characterization of N-rich copper nitride thin films: Role of chemical composition

(N-rich) Cu 3N polycrystalline films were deposited by DC triode sputtering from a copper target in a mixture of argon and nitrogen atmosphere. Their chemical composition, structure and electrical properties have been studied as a function of deposition parameters: nitrogen partial pressure ( P N 2 ) and DC bias. Depending on P N 2 and DC bias, the atomic nitrogen incorporated into the layers ranges from 26 at% to a limit value of 33 at% as measured by ion beam analysis (IBA) techniques. X-ray diffraction (XRD) data show that most of the layers are single phase, polycrystalline and with preferential 〈1 0 0〉 orientation. Optical and electrical measurements indicate that all layers present intrinsic semiconductor behavior with a thermal gap around 0.21–0.25 eV and a direct optical gap between 1.5 and 1.7 eV. The physical properties observed for these films are discussed in relation to nitrogen contents and sputtering parameters.

Structural and magnetic effects induced by annealing in sputtered thin films of R1-XCoX amorphous alloys

The objective of this work was to study the thermo-magnetic properties of sputtered R1-xCox amorphous alloys (R= Er, Tb, Sm). We have investigated a series of amorphous thin film of R1-xCox having a high Curie temperature Tc (above room temperature), which rises with Co content. The desired parameters were Tc higher than in crystalline state and low macroscopic anisotropy. Samples of R1-xCox have been prepared by DC triode sputtering from different targets. All of them have been then examined by means of X-ray diffraction for determining the as-cast amorphous structure and after each step of annealing, Rutherford back scattering (RBS) for determining the thickness and chemical composition. Magnetic measurements were taken before and after annealing (up to 400°C) at room temperature by means of vibrating sample magnetometer (VSM). These alloys were initially magnetically hard and characterized by a biaxial anisotropy in the film plane. Field annealing allowed to get both desired effects: first, reduction of internal stresses which were caused by the deposition process; second, producing a well-defined in plane anisotropy.

Structural and magnetic properties of triode-sputtered epitaxial γ′-Fe4N films deposited on SrTiO3 (001) substrates

Highly ordered, single-crystal Fe4N films were prepared on single-crystal SrTiO3 (001) substrates by reactive magnetically enhanced dc triode sputtering. Analytical techniques, including x-ray diffraction, reflectivity, ion channeling, and atomic force microscopy, were used to characterize the structure and morphology of the films. The magnetic properties of the films were measured by magnetic force microscopy and superconducting quantum interference device magnetometry. A technique that utilizes anisotropic magnetoresistance was employed for measurement of the magnetocrystalline anisotropy of the Fe4N films.

Perpendicular anisotropy detected by transversely biased initial susceptibility via the magneto-optic Kerr effect inFexSi1−xthin films andFexSi1−x/Simultilayers: Theory and experiment

We studied experimentally and theoretically the perpendicular anisotropy and the stripe-domain structure in both ${\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}$ thin films and ${\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}/\mathrm{Si}$ multilayers, the latter being in the low-modulation-length regime $(0.4\mathrm{nm}<\mathrm{\ensuremath{\lambda}}<7\mathrm{}\mathrm{nm}).$ The experimental study was made by means of the transversely biased initial susceptibility ${\ensuremath{\chi}}_{t\ensuremath{\beta}}$ via the magneto-optic Kerr effect. The samples under study were prepared by dc triode sputtering at ${T}_{S}=300\mathrm{K}.$ It is found that the appearance of stripe domains is more pronounced for decreasing \ensuremath{\lambda} as $x$ remains constant and may be caused by both the increase in effective magnetic thickness and the reduction in effective magnetization as \ensuremath{\lambda} decreases. For multilayers with $\ensuremath{\lambda}=0.4\mathrm{nm},$ the observed field dependence of ${\ensuremath{\chi}}_{t\ensuremath{\beta}}^{\ensuremath{-}1}$ is similar to that found in homogeneous thin films when weak stripe-domain structures arise as a consequence of the existence of perpendicular anisotropy ${K}_{N}.$ We propose a quasistatic one-dimensional model to explain the behavior of ${\ensuremath{\chi}}_{t\ensuremath{\beta}}^{\ensuremath{-}1}$ when stripe domains are present, and we analyze the critical occurrence of stripe domains. We calculated the so-called pseudo-uniaxial anisotropy field ${H}_{\mathrm{Ks}},$ associated with the stripes, in two extreme cases: exchange-driven susceptibility or magnetic free poles (nonzero divergence in the bulk). The latter case agrees better with experiment. We found that perpendicular anisotropy is not exclusive of a well-defined multilayer structure; i.e., ${K}_{N}$ arises even when there are no interfaces in the volume. By setting the experimental saturation field ${H}_{s}$ (obtained by hysteresis loops) into our model, we obtain both the perpendicular anisotropy constant ${K}_{N}{=10}^{4}--{10}^{5}{\mathrm{J}/\mathrm{m}}^{3}$ and the critical thickness ${t}_{c}$ for the occurrence of a stripe-domain structure. Some possible sources of perpendicular anisotropy are discussed, for example, the associated isotropic compressive stress \ensuremath{\sigma}, whose contribution is found to be $|{K}_{N}{|}_{\mathrm{magnetoel}}\ensuremath{\approx}1.5--4.5\ifmmode\times\else\texttimes\fi{}{10}^{4}{\mathrm{J}/\mathrm{m}}^{3}.$

Structural and magnetic properties of Ni/Cr multilayers

Ni/Cr multilayers have been grown on Si(100) by dc triode sputtering. Three different samples have been investigated where the only purposely variable parameter is the superperiod: Λ = 52, 35 and 27 Å. The Ni:Cr ratio was kept constant equal to 1:1 and the total thickness is about 1200 Å. The quality of the layering is shown by the low-angle X-ray diffraction spectra which exhibit both thickness fringes and Bragg peaks. At large angles, weak superlattice peaks appear around the 110 Cr/111 Ni diffraction peak. Pole figure measurements indicate a fiber texture: <111> for Ni and <110> for Cr. The average stress in the stackings has been evaluated via curvature measurements: the samples are in a high state of compressive stress, larger than 1 GPa. Systematic magnetization measurements have been performed with a vibrating sample magnetometer as a function of temperature with the applied field parallel or perpendicular to the sample plane. All the multilayers exhibit in-plane anisotropy. The magnitude of the saturation magnetization indicates an important Ni-Cr intermixing at the interfaces. The temperature behaviour of the magnetic moment indicates two-dimensional effects.

Characteristic Structures of Ce-Based Amorphous Heavy Fermion Systems

X-ray diffractions are measured for Ce–Cu, Ce–Ru and Ce–Si amorphous alloys produced by DC triode sputtering. The radial distribution functions, RDF’s, are derived from these measurements and compared with RDF of the intermetallics with nearly the same compositions as those of the amorphous alloys. The short range structures of the Ce–Cu and Ce–Si amorphous alloys are chemically ordered ones in the nearest neighbor ranges, resembling their crystalline counterparts. The short range structures of the Ce–Ru amorphous alloys, on the other hand, are disordered ones, being different from those of their crystalline counterpart. The structure characteristics are discussed with their low temperature physical properties similar and dissimilar to those of the crystalline counterparts.

Giant magnetoresistance in sputtered (Co70Fe30)xAg1-x heterogeneous alloys

We report the structural, magnetic and transport properties of (Co70Fe30)xAg1-x heterogeneous alloys, with x varying between 27 and 47 at.%. The samples were prepared by DC triode sputtering at room temperature (RT) and liquid-nitrogen temperature. Annealing processes lead to phase segregation and grain growth, resulting in the formation of small and compact Co70Fe30 precipitates. The resulting evolution of the magnetic properties has been investigated by SQUID magnetometry, Mossbauer spectroscopy and ferromagnetic resonance. The largest magnetoresistance amplitudes at room temperature have been obtained for a magnetic concentration x of around 36 at.% in both as-deposited and annealed samples. Amplitudes Delta R/R(H=0) of 15% in the as-deposited samples and 21% in samples annealed at 600 K for 10 min have been observed at RT. At 4 K these amplitudes reach 43% (equivalent to Delta R/R(H=2 T)=75%).

Magnetostrictions and Magnetic Properties of Fe-Co-RE (RE: Rare Earth Elements) Films Produced by DC Triode Sputtering

Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</inf> Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</inf> alloy has a large magnetostriction value and a high saturation magnetization. We have investigated the magnetostriction and magnetic properties of bec Fe-Co-RE (RE a rare earth element) films. These films were prepared by dc triode sputtering. Addition of the RE elements Pr and Tb was found to increase the magnetostriction, while addition of the RE elements Ce, Nd, Sm and Er decreased it. These alloy films all exhibited high saturation magnetization values in excess of 200 emu/g. The high saturation magnetization appeared on addition of a small percentage of the RE element. Such films may be useful as soft magnetic materials.

Structural and magnetic studies in Ni/Ti multilayers

Structural and magnetic studies have been carried out on Ni/Ti multilayers prepared by DC triode sputtering. Both metal layers are crystalline with a (111) fibre structure when they are thicker than 20 Å. But for thinner layers one observes a solid solution with an amorphous-like structure. The magnetization decreases with t(Ni) and the analysis of the results at 5 K indicates the presence of a dead Ni layer about 12 Å thick. The t(Ni) dependence of the effective anisotropy shows the absence of surface anisotropy contribution.

Annealing effects on the structure and magnetic properties of Ni/Ti multilayers

Interfaces of Ni-Ti multilayers deposited by dc triode sputtering under high purity conditions (base pressure 10 -7 Torr plus getter-sputtering) and their thermal evolution are studied. This was achieved by combining high energy electron diffraction, secondary ion mass spectrometry and magnetometry. The study shows the existence of a non-magnetic interfacial amorphous layer due to interdiffusion over very short distances during deposition. A marked asymmetry between the two sides of a given layer is observed, due to interfacial contamination of Ti by C and O acting as a diffusion barrier. Annealing treatments yield an increase in amorphization and finally crystallization of the interfacial amorphous phase to a NiTi stable phase.

Magnetic and magneto-optical properties of NdFeB/Mo and NdFeB/FeB amorphous bilayers

Magnetic and magneto-optical properties of NdFeB/Mo and NdFeB/FeB amorphous bilayers, grown by dc triode sputtering on cooled glass substrates, were studied. Transverse Kerr effect, transverse biased initial susceptibility and SQUID magnetometry measurements were performed. Glass/film interface effects, regarding magnetization and anisotropies (dead layers, isotropic sublayers), were found in NdFeB films.

Ｆｅ‐Ｃｏ‐ＲＥ（ＲＥ：希土類金属）系ＤＣ３極スパッタ膜の磁歪および磁気特性

The Fe0.7Co0.3 alloy has a large magnetostriction value and a high saturation magnetization. We have investigated the magnetostriction and magnetic properties of bcc Fe-Co-RE (RE: rare earth elements). These films were prepared by DC triode sputtering method. An addition of the RE elements Pr and Tb Were found to increase the magnetostriction value, while the addition of RE elements Ce, Nd, Sm and Er decreased it. These alloy films all exhibited a high saturation magnetization value, greater than 200 emu/g. This occured upon an addition of a small percentage of the RE element. These films may be useful as soft magnetic materials.

The Effect of Addition of Rare Earth Elements on Magnetostriction in bec Fe-Co Alloys

The magnetostriction and magnetic properties of bcc Fe-Co-Sm alloys produced by dc triode sputtering have been investigated. Addition of 3 at% Sm suppressed the large positive magnetostriction of bec Fe-Co alloys, resulting in almost zero magnetostriction for bcc Fe 0.7 C 0.3 alloys. These nonmagnetostrictive alloys show a high saturation magnetization of about 210 emu/g, and thus are thought to be useful as soft magnetic materials.

Heavy-fermion behavior in amorphous and crystallized CeCu 6 alloys produced by sputter deposition

Amorphous CeCu 6 alloys have been produced by dc triode sputtering. Its remarkable enhancement of the electronic specific heat coefficient indicates heavy-fermion characteristics at low temperatures, however, the temperature dependence of the magnetic susceptibility and electrical resistivity indicate no coherent Fermi condensation down to 2 K, in contrast to the typical heavy-fermion characteristics in the crystallized CeCu 6 alloys.

Microstructural and magnetic characterization of the interfaces in DC triode sputtered metal/carbon and metallic multilayer films

Metal/carbon (Ni/C, Co/C, Fe/C, permalloy/C) and metallic multilayers (Fe/Ni, Fe/Co, Ni/Ti) have been prepared by low energy DC triode sputtering under computer-controlled conditions. The magnetic properties are shown to be related to the structural characteristics of the films, such as the existence of an interfacial amorphous layer in metal/carbon multilayers, or the formation of a single phase structure in very thin metallic multilayers, due to interdiffusion at the interfaces.

Ｆｅ‐Ｃｏ合金の磁歪の希土類元素添加による制御

Magnetostriction and magnetic properties of bcc Fe-Co-Sm alloys produced by DC triode sputtering method were investigated. An addition of 3 at% Sm suppressed large positive magnetostriction of bcc Fe-Co alloys, resulting in almost zero magnetostriction in the vicinity of bcc Fe0.7C0.3 alloys. These nonmagnetostrictive alloys show a high saturation magnetization of about 210 emu/g, and thus are thought to be useful for soft magnetic materials.

Structural and magnetic properties of Fe/Ni and Fe/Co multilayers

Fe/Ni and Fe/Co multilayers (ML) have been deposited by dc triode sputtering, with a layer thickness (t) in the range 1–10 nm. For t≳4 nm both metals are in crystalline form (bcc Fe, fcc Ni, hcp Co). For t&amp;lt;2 nm one has a single-phase structure (fcc in Fe/Ni ML, bcc in Fe/Co ML) which can be explained by assuming the presence of a 1-nm-thick mixed layer at the interfaces. This interfacial mixing affects the magnetic properties. The basic difference between the two systems is the fact that while Fe-Ni interfacial alloys are magnetically soft those of Fe-Co are hard which leads to different magnetic behavior. Furthermore, the Fe layers are better crystallized in our samples than those prepared by rf magnetron or ion-beam sputtering.