The switching process of granular Co nanowires is investigated using the finite element method. The wires have a diameter of 55 nm and a length of 1000 nm. Transmission electron microscopy (TEM) investigations show two different types of hcp-structured grains. For one, the c axis is randomly oriented in a plane perpendicular to the long axis of the wire, and the other has the c axis parallel to the long axis. The numerical results show that finite element micromagnetics can explain the influence of the microstructure in magnetic nanosystems.
Power MOSFETs have been primarily designed for switching applications, in which case they are operated to the best extent possible either at zero drain to source voltage or at zero drain current. Accordingly, datasheets provide parametric information including input, output and reverse parasitic capacitance at zero current level. When used in linear condition however, both drain to source voltage and drain current are non-zero at the same time, leaving open the question of the parasitic capacitance levels. The present paper reports relevant parameter measurements performed on a MOSFET available for linear control within power units on board of satellite. A parasitic capacitance increase by up to one order of magnitude is highlighted for non-zero currents, in particular between drain and source. The pattern has been confirmed by measurements on two additional MOSFETs. The attention of designers is therefore drawn on such feature as parasitic capacitance may significantly affect the performances of their designs, e.g. in terms of feedback control stability or conducted susceptibility for series regulator, or in terms of speed when switching in between zero current and zero voltage conditions.
Vortex nucleation and vortex motion are the main mechanisms of magnetization reversal in micrometer-sized magnetic elements. The critical field required to nucleate a vortex depends on the temperature. We propose a method that combines standard Landau-Lifshitz-Gilbert (LLG) micromagnetics and an elastic band method to simulate nonzero temperature hysteresis curves of magnetic thin film elements. Whereas the LLG simulations gives the equilibriums states before and after a vortex enters the element, the elastic band method gives the height of the energy barrier between these two states. Thus temperature-dependent nucleation fields can be computed without the need to perform stochastic LLG simulations.
Devices based on bipolar resistive switching in solid electrolytes are among the promising emerging memory technologies. Information storage is based on stable formation and removal of conductive links during electrical operation. In this paper, development results achieved during a joint project of Qimonda AG and ALTIS Semiconductor including the characterization of single cells and electrical data from recently processed 2Mbit memory array devices based on 90 nm CMOS technology node are presented. The unique combination of low-power, non-volatile, and fast operation for CBRAM will be shown. Measured data will demonstrate the excellent multi-level capability promoting the competitiveness with existing technologies in terms of bit density. Furthermore, technology challenges and memory application relevant features like endurance, retention, and operating temperature will be discussed.
Recent experimental studies on the switching behaviour of Co∕Pd multilayer islands with sizes in a range from 20–100 nm shows the classical angular dependence for uniform rotation. We compare measured angular dependence of the switching field with micromagnetic finite element simulations. Simulation results show reversal modes close to uniform rotation for islands smaller than 30 nm. Larger islands (>70nm) reverse by nucleation of a reversed domain followed by domain wall propagation. However, the angular dependence does not change its character with the island size. The nucleation of the reversed domain determines the switching field.
Patterned media shows great potential for future ultrahigh-density magnetic recording. The thermal stability is determined by the relevant transition states. We apply the nudged elastic band method to calculate energy barriers and thermal reversal modes as a function of the island size and intergrain exchange coupling. Nonuniform reversal modes and transition states are found even in single-domain islands. The resulting energy barriers are significantly lower than those estimated from simplified reversal modes.
