Sheldon Schultz

Bio: Sheldon Schultz is an academic researcher from University of California, San Diego. The author has contributed to research in topics: Magnetization & Plasmon. The author has an hindex of 43, co-authored 135 publications receiving 26175 citations. Previous affiliations of Sheldon Schultz include University of California & École Polytechnique Fédérale de Lausanne.

Fabrication and Characterization of High Aspect Ratio Perpendicular Patterned Information Storage Media in an Al2O3/GaAs Substrate

Abstract: In a new approach, we have fabricated 6:1 aspect ratio magnetic nanocolumns, 60–250 nm in diameter, embedded in a hard aluminum-oxide/gallium-arsenide (Al2O3/GaAs) substrate. The fabrication technique uses the highly selective etching properties of GaAs and AlAs, and highly efficient masking properties of Al2O3 to create small diameter, high aspect ratio holes. Nickel (Ni) is subsequently electroplated into the holes, followed by polishing, which creates a smooth and hard surface appropriate for future reading and writing of the columns as individual bits for high density information storage. We have used magnetic force microscopy and scanning magneto-resistance microscopy to characterize the resulting magnets. We find the columns more magnetically stable than previously achieved with magnets embedded in a SiO2 substrate. Such stability is necessary before further writing of perpendicular patterned media can be demonstrated.

Magnetization decay in Co‐Cr films

Abstract: We have measured magnetization time decay in perpendicularly oriented Co‐Cr films over seven time decades as a function of field and temperature The anomalous Hall coefficient of the sample itself, which is proportional to the magnetization within the sample, is used to determine the magnetization Magnetization time decay measurements made with this technique, for times>10 s, agree with vibrating‐sample magnometer (VSM) data taken at 77 and 300 K, but can be made as soon as 2 ms after turning off the external magnetic field used to saturate the sample The principle features of magnetization decay in Co‐Cr are as follows: (1) The magnetization time decay in Co‐Cr films is nearly independent of external field over a range of several kG, unlike particulate media, where the magnetization decay rate is sharply peaked around the coercive field (2) At 300 K, the magnetization time decay deviates markedly from log t, with the decay per decade of time dropping by almost a factor of 2 between 10−3 and 104 s (3

Measuring the coercivity of individual sub-micron ferromagnetic particles by Lorentz microscopy

Abstract: The Foucault mode of Lorentz microscopy has been applied to detect the polarity of the magnetic field produced by ferromagnetic particles in the single-domain size range. One can follow the polarity of any given particle through multiple cycles of removal and return of the sample from the transmission electron microscope. Hence, one can determine the particle coercivity by applying a sequence of known fields to the sample. The proposed technique makes it possible to obtain unambiguous data for the dependence of an individual particle's coercivity on the orientation of the applied field, and the particle's dimensions. Both these data are needed to determine the magnetization reversal mechanism in single-domain particles. The authors demonstrate the ability to detect the polarity and measure the coercivity of nearly ellipsoidal gamma -Fe/sub 2/O/sub 3/ particles which have a moment of approximately 10/sup -13/ emu. >

ESR in a heavy-fermion alloy (UBe13) doped with local moments.

Abstract: We have determined the ESR properties of UBe13 doped with dilute local moments of Er, Dy, or Gd over the temperature region where there is a large variation in the enhanced specific heat. We find that neither the enhancement, the temperature variation, nor any other anomalous behavior appears to be mirrored in the ESR data. We suggest that this unexpected result must be incorporated into current models of heavy-fermion systems. © 1985 The American Physical Society.

Surface plasmon subwavelength optics

Abstract: Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

Spintronics: Fundamentals and applications

Abstract: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

Experimental Verification of a Negative Index of Refraction

Abstract: We present experimental scattering data at microwave frequencies on a structured metamaterial that exhibits a frequency band where the effective index of refraction (n) is negative. The material consists of a two-dimensional array of repeated unit cells of copper strips and split ring resonators on interlocking strips of standard circuit board material. By measuring the scattering angle of the transmitted beam through a prism fabricated from this material, we determine the effective n, appropriate to Snell's law. These experiments directly confirm the predictions of Maxwell's equations that n is given by the negative square root of epsilon.mu for the frequencies where both the permittivity (epsilon) and the permeability (mu) are negative. Configurations of geometrical optical designs are now possible that could not be realized by positive index materials.

Plasmonics for improved photovoltaic devices

Abstract: The emerging field of plasmonics has yielded methods for guiding and localizing light at the nanoscale, well below the scale of the wavelength of light in free space. Now plasmonics researchers are turning their attention to photovoltaics, where design approaches based on plasmonics can be used to improve absorption in photovoltaic devices, permitting a considerable reduction in the physical thickness of solar photovoltaic absorber layers, and yielding new options for solar-cell design. In this review, we survey recent advances at the intersection of plasmonics and photovoltaics and offer an outlook on the future of solar cells based on these principles.

Controlling Electromagnetic Fields

Abstract: Using the freedom of design that metamaterials provide, we show how electromagnetic fields can be redirected at will and propose a design strategy. The conserved fields-electric displacement field D, magnetic induction field B, and Poynting vector B-are all displaced in a consistent manner. A simple illustration is given of the cloaking of a proscribed volume of space to exclude completely all electromagnetic fields. Our work has relevance to exotic lens design and to the cloaking of objects from electromagnetic fields.