Electron beam patterned permalloy circular dots of 700 nm diameter with small separations were studied by magnetic force microscopy (MFM) in the presence of an in situ magnetic field. Images in the demagnetized state show that the dot is in a vortex state with a vortex core (singularity) in the center. Local hysteresis loops, measured by cantilever frequency shift in an external field, indicate that the magnetization reversal of individual disks is a vortex nucleation and annihilation process. By carefully doing MFM, nucleation and annihilation fields without MFM tip stray field distortions are obtained. Configurational anisotropy originated from magnetostatic coupling is found through hysteresis loops. © 2002 American Institute of Physics

The methanol‐, ethanol‐, and 1‐propanol‐amylose “V” complexes have been prepared and their unit cell dimensions calculated from their x‐ray powder patterns. The small unit cell (with 13.0 A. helix diameter), previously reported to occur only after the complete removal of water, has been observed for the wet methanol and ethanol complexes. In fact, a methanol complex containing as much as one mole of water per glucose residue had the small unit cell. Residual water and residual complexing agent analyses have shown that complexes dried to constant weight under stringent conditions retain as much as one mole of water and one‐quarter mole of complexing agent per helix turn. It has been concluded that the specific organic complexing agent plays an important role in dictating the unit cell size.

Reactive sputtering has been found to be a desirable method for the preparation of conductive manganese dioxide films. The major parameter determining conductivity and the oxide of manganese formed by reactive sputtering is substrate temperature. At substrate temperatures in excess of approximately 350°C, low‐conductivity lower oxides of manganese are formed. The infrared spectrum of films is sensitive to variations in the stoichiometry of the oxides and is a valuable tool for the characterization of manganese oxide thin films.

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The magnetic properties of rf sputtered Ni81Fe19 films were studied as a function of thickness from <100 to ∼1200 Å. In contrast to some recently reported studies, there was no evidence of an oscillatory dependence of resistivity on Δρ as a function of thickness. The magnetoresistance, resistance, coercivity, and anisotropy field varied smoothly with thickness. In contrast, the magnetostriction λs had a minimum of −1.5×10−6 at ∼300 Å. The saturation magnetic moment did not decrease with thickness over the thickness range studied here. The derived magnetoresistance of an ‘‘infinitely’’ thick film was 3.92% compared to the bulk value of ∼4%. The analysis indicates that surface and grain-boundary scattering are the primary cause of lower than bulk values of magnetoresistance in these thin permalloy films.