Relating surface roughness and magnetic domain structure to giant magneto-impedance of Co-rich melt-extracted microwires.

Understanding the relationship between the surface conditions and giant magneto-impedance (GMI) in Co-rich melt-extracted microwires is key to optimizing their magnetic responses for magnetic sensor applications. The surface magnetic domain structure (SMDS) parameters of ~45 µm diameter Co69.25Fe4.25Si13B13.5-xZrx (x = 0, 1, 2, 3) microwires, including the magnetic domain period (d) and surface roughness (Rq) as extracted from the magnetic force microscopy (MFM) images, have been correlated with GMI in the range 1-1000 MHz. It was found that substitution of B with 1 at. % Zr increased d of the base alloy from 729 to 740 nm while retaining Rq from ~1 nm to ~3 nm. A tremendous impact on the GMI ratio was found, increasing the ratio from ~360% to ~490% at an operating frequency of 40 MHz. Further substitution with Zr decreased the high frequency GMI ratio, which can be understood by the significant increase in surface roughness evident by force microscopy. This study demonstrates the application of the domain period and surface roughness found by force microscopy to the interpretation of the GMI in Co-rich microwires.

Probing photonic Bloch wavefunctions with plasmon-coupled leakage radiation.

We demonstrate theoretically and experimentally the direct observation of photonic Bloch wavefunctions in dielectric loaded plasmonic crystals. The ultimate ability to observe the Bloch wavefunctions in the surface emission images depends not on the light diffraction through the holes but on the strength of the in-plane light scattering from the individual lattice features and the presence of the metal layer which allows the light propagating within the crystal to be imaged in the far-field. Experimental results are in excellent agreement with simulated surface emission and back focal plane images of plasmonic crystals.