Showing papers by "Thomas J. Silva published in 1996"
TL;DR: In this article, an abrupt and large increase in the absolute magnitude of λs in sputtered polycrystalline permalloy (Ni81Fe19) films for thicknesses below 7 nm was observed.
Abstract: An abrupt and large increase in the absolute magnitude of λs in sputtered polycrystalline permalloy (Ni81Fe19) films for thicknesses below 7 nm was observed. Permalloy films maintain near‐zero magnetostriction with film thicknesses above 7 nm. Film surface studies and microstructural characterizations suggest that the magnetostriction observed in this study is possibly due to an altered surface morphology of microstructural origin. This observation appears to be critical from the viewpoint of permalloy‐based giant magnetoresistive or spin‐valve sensor fabrication where typical permalloy film thicknesses are 3–10 nm. Because thin films with nonzero magnetostriction can induce an undesirable magnetoelastic anisotropy during sensor operation, the control and adjustment of the film composition seems necessary to minimize magnetostriction.
65 citations
TL;DR: In this article, the design and implementation of a scanning near-field optical microscope expressly intended for the imaging of magnetic domains in reflection with subwavelength resolution is described, and the results of two tests of the microscope performance are presented.
Abstract: The design and implementation of a scanning near‐field optical microscope expressly intended for the imaging of magnetic domains in reflection with subwavelength resolution is described. The microscope employs ∼40 nm silver particles optically excited at the plasmon resonance as the near‐field probes. Special attention is given to the Newton ring interferometer used to regulate the separation between the near‐field probe and the sample. The results of two tests of the microscope performance are presented. The first is a measurement of the dependence of the near‐field magneto‐optic Kerr effect on probe/sample spacing for a longitudinally magnetized metallic thin film. The effect decreases rapidly with increasing separation with a length scale comparable to the probe size. The second is a series of images of a domain in a perpendicularly magnetized multilayer metallic film at different probe/sample spacings. The images indicate a persistent effect with increasing separation but diminishing resolution. Fundamental differences between the near‐field magneto‐optic Kerr effect for perpendicularly and longitudinally magnetized samples is discussed. An estimate is made as to the fundamental limit of resolution with this particular form of near‐field microscopy.
46 citations
TL;DR: In this article, second-harmonic magneto-optic Kerr measurements on polycrystalline Ni81Fe19 thin films, ranging in thickness from 1 nm to 2 μm, on Al2O3 coated Si (001).
Abstract: We report second‐harmonic magneto‐optic Kerr measurements on air‐exposed, polycrystalline Ni81Fe19 thin films, ranging in thickness from 1 nm to 2 μm, on Al2O3 coated Si (001). For samples thicker than 20 nm, in the transverse Kerr geometry, we observe a factor of 4 change in second‐harmonic intensity upon magnetization reversal. For thin samples, we observe interference between second‐harmonic fields from the various interfaces and deterioration of ferromagnetism in the 1 and 2 nm films. Modeling suggests that the Ni81Fe19/Al2O3 interface has a larger second‐order susceptibility than the air/Ni81Fe19 surface.
24 citations
TL;DR: In this paper, the second harmonic magneto-optic Kerr effect was measured in both transverse and longitudinal geometries from Ni/sub 81/Fe/sub 19/ films.
Abstract: We report measurements of the second-harmonic magneto-optic Kerr effect in both transverse and longitudinal geometries from 100-nm-thick Ni/sub 81/Fe/sub 19/ films. For the transverse geometry, we observe intensity changes of roughly a factor of 3 upon magnetization reversal. In the longitudinal geometry, the second harmonic Kerr angle is 32.6/spl deg/ for s-incidence and 6.8/spl deg/ for p-incidence. A simple theoretical treatment allows us to compare the relevant second-order susceptibility elements as measured in the two geometries: the element magnitudes and relative phase shifts agree within experimental error.
11 citations