ALBERT

Notes: a:C–Nx films were deposited on Si(111) wafers at ambient temperatures by reactive magnetron sputtering of C in a mixed Ar/N2 discharge. The hardness (H) and elastic modulus (E) were assessed via nanoindentation using a Berkovich diamond indenter. The nitrogenated films exhibited increased hardness and elastic moduli values compared to the amorphous carbonated films, i.e., 25 and 240 GPa to 16 and 160 GPa, respectively. A sphere-on-flat (magnetic tape) wear tester was used to assess wear scar volume losses as a function of wear time. All films were in a state of compression (intrinsic and thermal stress). The bonding, composition, and structure of the films for all the deposition conditions were assessed by micro-Raman spectroscopy, energy dispersive x-ray spectroscopy (EDX), and x-ray diffraction (XRD), respectively, and subsequently correlated to overall film properties.© 1997 American Institute of Physics.

Notes: An analysis of room temperature electrical transport properties in sputtered (Co90Fe10/Ag) giant magnetoresistive multilayers is presented. The Co90Fe10 and Ag thickness ranges are both well below bulk electron mean free paths. Layer thickness dependent resistivity is observed and compared to resistivity measurements of single layer Co90Fe10 and Ag films. © 1997 American Institute of Physics.

Notes: We have studied the film thickness dependence of the remanent magnetization (delta M plots), the magnetic viscosity, and the activation volumes of Fe thin films sputtered on commercial nanochannel alumina of 20 nm average pore diameter. The films have the form of a contiguous interconnected network. A critical film thickness of φ∼20 nm defines two regions with very different magnetic behavior. For this critical value of φ we have found a maximum in the remanent coercivity, a minimum in the interparticle interaction parameter α, and a rapid increase in the magnetic viscosity, the irreversible susceptibility and the activation volume. Our results are interpreted in terms of the pinning effects caused by nonmagnetic inclusions. The functional relationship between the remanent coercivity and the activation volume is similar to the one found in long cylinders that reverse magnetization by a curling mechanism. © 1997 American Institute of Physics.

Notes: Giant magnetoresistance (GMR), crystal structure, and magnetic properties have been investigated in sputtered Ni66Fe16Co18-Ag/Cu hybrid granular multilayer thin films. High angle x-ray diffraction (HXRD) was used to reveal the overall film structure and growth texture and low angle XRD was used to investigate the periodicity and flatness of the multilayer structures. Hysteresis loops for the as-deposited Ag-rich films show superparamagnetic behavior (and conventional granular GMR) which does not saturate in 14 kOe. Very NiFeCo-rich films are magnetically soft and exhibit induced in-plane uniaxial anisotropy.

Notes: Films of Fe, Co, and Co35Fe65 alloy have been sputter deposited onto the surface of porous nanochannel alumina substrates producing nanostructured contiguous magnetic "networks." Large room temperature coercivities have been measured which approximately scale with the bulk saturation magnetization of the material used. In the as-deposited state the largest coercivities (e.g., 〉1000 Oe for Co35Fe65) are observed in ∼15-nm-thick networks deposited on the smallest commercially available pore size substrates (those having an average pore diameter of ∼20 nm and a wall thickness of ∼15 nm). Preliminary studies of the effects of annealing indicate that coercivities can be substantially increased (by as much as ∼50%) with an appropriate post-deposition thermal treatment. © 1997 American Institute of Physics.

Notes: As-deposited, magnetically soft nanocrystalline FeTaN films are successfully grown by dc-magnetron reactive sputtering. Growth conditions are instrumental in extending the solubility limit of Ta in the bcc FeTa alloy. Nitrogen incorporation in FeTa films is found to be much higher than in Fe films and can be explained in terms of thermochemistry using a large Ta-N interaction coefficient. The influence of different alloying elements is discussed theoretically, with regard to the metal-nitrogen affinity. A "typical columnar microstructure'' associated with the sputtering process is identified and its evolution versus the extent of nitrogenation is described in detail. Stress, magnetostriction, resistivity, and magnetic properties are respectively described as a function of both Ta and N contents of the films. The magnetic behavior of as-deposited nanocrystalline FeTaN is found to be very sensitive to both the dimension of the grains, their morphology and the nature of the grain boundary material which represents a non-negligible volume fraction in nanocrystalline films. It is proposed that the columnar structure plays the key role in promoting a large perpendicular anisotropy component (K⊥) and controls a "Stripe Domain''-like behavior observed at high N contents, which cannot be explained in terms of film stress in this material. The contribution of the magnetoelastic anisotropy is also described. In summary, by breaking the columnar structure, the incorporation of nitrogen first decreases K⊥ below the critical limit for formation of stripe domains. In these conditions, N acts as a "grain refiner'' and excellent soft magnetic behavior is reported and explained in terms of "vanishing magnetocrystalline anisotropy.'' The good thermal stability of such soft films is confirmed. By contrast, higher nitrogen incorporation increases K⊥ above the critical limit, leading to a stable stripe domain-like structure which does not allow for soft magnetic properties. This phenomenon has been found to be reversible at low temperature where a complete restoration of the soft magnetic behavior has been observed. This anomalous result is explained by the transformation of the grain boundary material into a "low Curie temperature phase'' for large N contents. © 1996 American Institute of Physics.

Notes: Magnetoresistance and magnetic hysteresis in NiFeCo/Cu soft magnetic multilayers with a fixed number of bilayers (six) and magnetic and spacer layer thickness but varying composition has been studied. The highest value of the transverse GMR obtained is 6.8% in a saturation field of ≈40 Oe at room temperature. Very high sensitivity, around 1%-2%/Oe and unconventional easy-axis hysteresis and GMR loop shapes have been observed. The analysis of the GMR effects and the associated hysteretic behavior by using a model that includes biquadratic exchange coupling suggests that the samples are composed of at least two distinctively different parts.

Notes: The thermal evolution of structure, giant magnetoresistance (GMR), and magnetic properties in two sequences of sputtered (Co90Fe10/Ag) multilayers is presented. Granular-type and "discontinuous'' GMR is observed depending on layer thickness. © 1996 American Institute of Physics.

Notes: Domain structures in thin-film heads can be significantly influenced by magnetoelastic anisotropy. In this study we have undertaken systematic measurements of magnetostriction and stress in as-deposited and annealed states in FeN and FeTaN single-layer thin films with varying nitrogen contents. Magnetostriction was positive for FeN films, increased with increasing nitrogen content, and shifted toward negative values after annealing. Stress in as-deposited FeN films was tensile and decreased (became more compressive) with increasing nitrogen content. Annealing the FeN films resulted in significant stress relief. By contrast, magnetostriction was found to be negative for simple FeTa (zero nitrogen) and increased linearly with increasing nitrogen content to positive values. The magnetostriction in FeTaN did not change significantly after annealing at 200 and 250 °C. FeTaN film stresses were compressive in the as-deposited state and increased in magnitude (became more compressive) with increasing nitrogen content. After annealing these stresses were relieved slightly. Ta has been found to be very effective in enhancing the thermal stability of the FeN films. © 1996 American Institute of Physics.

Notes: FeTaN single layer and FeTaN/SiO2 multilayer films were grown by high rate reactive dc magnetron sputtering. The film geometry (FeTaN layer thickness, SiO2 spacer thickness, and number of bilayer units) dependence of the structure, magnetic properties and high-frequency permeability characteristics were investigated.