A microactuator technology that combines magnetic thin films with polysilicon flexural structures is described. Devices are constructed in a batch-fabrication process that combines electroplating with conventional lithography, materials, and equipment. A microactuator consisting of a 400x(47-40)x7 µm 3 rectangular plate of NiFe attached to a 400x(0.9-1.4)x2.25 µm 3 polysilicon cantilever beam has been displaced over 1.2 mm, rotated over 180°, and actuated with over 0.185 nNm of torque. The microactuator is capable of motion both in and out of the wafer plane and has been operated in a conductive fluid environment. Theoretical expressions for the displacement and torque are developed and compared to experimental results.
Soliton return effect in an annular Josephson junction and nonzero minimum voltage and current in the current step Solutions of the equation of motion of Josephson junction devices are approximated by analytical relations in the pronounced nonlinear range of small voltages. The minimum current at which the junction switches back into the net zero voltage state is established for devices with resistive and inductive elements, including the nonlinear tunnel resistance of the junction. The stability of the voltage state is estimated. Conditions for which junctions fail to enter the zero-voltage state are discussed. We obtain the equation of motion by setting all currents Ie __ c R(V) J L FIG. 1. Equivalent circuit of the devices considered here. The element J represents the Josephson current generator 1m sin>. The other elements include those of the junction in parallel with possible external elements. The resistance which contains the nonlinear tunnel resistance of the junction is voltage dependent.
Approximate formulas that yield the resonance amplitude of symmetric two-junction interferometers have been derived using step-by-step linearizations and approximations based on physical arguments. The resonance amplitude is found to strongly depend on the device Q. It increases as Q increases. reaches a peak. and subsequently decreases again. In the low-Q region. the resonance step is very broad and largely independent of rapid changes in device current. This is not the case in the high-Q region where the resonance amplitUde increases with decreaSing device current rise time. In the range of validity of the approximations. the results were compared to computer solutions. and reasonable agreement was found for arbitrarily chosen test cases. Although derived for two-junction interferometers. the results can be extended directly to certain symmetric three-junction interferometers.PACS numbers: 74.50.+r. 85.25.+k
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