N. More

Bio: N. More is an academic researcher from IBM. The author has contributed to research in topics: Superlattice & Magnetoresistance. The author has an hindex of 2, co-authored 2 publications receiving 2125 citations.

Oscillations in exchange coupling and magnetoresistance in metallic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr.

Abstract: We report the discovery of antiferromagnetic interlayer exchange coupling and enhanced saturation magnetoresistance in two new metallic superlattice systems, Co/Cr and Co/Ru. In these systems and in Fe/Cr superlattices both the magnitude of the interlayer magnetic exchange coupling and the saturation magnetoresistance are found to oscillate with the Cr or Ru spacer layer thickness with a period ranging from 12 \AA{} in Co/Ru to \ensuremath{\simeq}18--21 \AA{} in the Fe/Cr and Co/Cr systems.

Giant magnetoresistance in sputtered magnetic superlattices (invited) (abstract)

Abstract: Recently, large values of saturation magnetoresistance (SMR) were reported in single‐crystal Fe/Cr superlattice structures prepared by molecular‐beam‐epitaxy (MBE) techniques.1 We have prepared similar polycrystalline superlattice structures by dc magnetron sputtering in a high‐vacuum deposition system and find comparably high SMR values of up to 50% for Cr‐layer thicknesses of ≂8 A. Magnetization‐versus‐field data suggest that successive Fe layers are coupled antiferromagnetically with one another, as for the MBE‐grown films. Magnetic fields of up to 20 kOe are required to align Fe layers 20 A thick, implying substantial exchange‐coupling energies between the Fe layers. While the magnetization curves have a weak temperature dependence even for temperatures above the Neel temperature of bulk Cr, the SMR decreases as the temperature is increased. Work on related structures which do and do not show giant SMR effects will be discussed.

Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers

Abstract: Magnetically engineered magnetic tunnel junctions (MTJs) show promise as non-volatile storage cells in high-performance solid-state magnetic random access memories (MRAM). The performance of these devices is currently limited by the modest (< approximately 70%) room-temperature tunnelling magnetoresistance (TMR) of technologically relevant MTJs. Much higher TMR values have been theoretically predicted for perfectly ordered (100) oriented single-crystalline Fe/MgO/Fe MTJs. Here we show that sputter-deposited polycrystalline MTJs grown on an amorphous underlayer, but with highly oriented (100) MgO tunnel barriers and CoFe electrodes, exhibit TMR values of up to approximately 220% at room temperature and approximately 300% at low temperatures. Consistent with these high TMR values, superconducting tunnelling spectroscopy experiments indicate that the tunnelling current has a very high spin polarization of approximately 85%, which rivals that previously observed only using half-metallic ferromagnets. Such high values of spin polarization and TMR in readily manufactureable and highly thermally stable devices (up to 400 degrees C) will accelerate the development of new families of spintronic devices.

The emergence of spin electronics in data storage

Abstract: Electrons have a charge and a spin, but until recently these were considered separately. In classical electronics, charges are moved by electric fields to transmit information and are stored in a capacitor to save it. In magnetic recording, magnetic fields have been used to read or write the information stored on the magnetization, which 'measures' the local orientation of spins in ferromagnets. The picture started to change in 1988, when the discovery of giant magnetoresistance opened the way to efficient control of charge transport through magnetization. The recent expansion of hard-disk recording owes much to this development. We are starting to see a new paradigm where magnetization dynamics and charge currents act on each other in nanostructured artificial materials. Ultimately, 'spin currents' could even replace charge currents for the transfer and treatment of information, allowing faster, low-energy operations: spin electronics is on its way.

Giant magnetoresistance in heterogeneous Cu-Co alloys.

Abstract: We have observed giant magnetoresistance in heterogeneous thin film Cu-Co alloys consisting of ultrafine Co-rich precipitate particles in a Cu-rich matrix. The magnetoresistance scales inversely with the average particle diameter. This behavior is modeled by including spin-dependent scattering at the interfaces between the particles and the matrix, as well as the spin-dependent scattering in the Co-rich particles.

Fabrication and Magnetic Properties of Arrays of Metallic Nanowires

Abstract: Arrays of ferromagnetic nickel and cobalt nanowires have been fabricated by electrochemical deposition of the metals into templates with nanometer-sized pores prepared by nuclear track etching. These systems display distinctive characteristics because of their one-dimensional microstructure. The preferred magnetization direction is perpendicular to the film plane. Enhanced coercivities as high as 680 oersteds and remnant magnetization up to 90 percent have also been observed.