Tubular modular permanent-magnet machines equipped with quasi-Halbach magnetized magnets - Part II: Armature reaction and design optimization

Using the analytical formulas derived in Part I for predicting the magnetic field distribution, thrust force, and electromotive force of a three-phase tubular modular permanent-magnet machine equipped with quasi-Halbach magnetized magnets, this paper analyzes the armature reaction field, and addresses issues that are pertinent to the design optimization of the machine. It shows that optimal values of the ratio of the axial length of the radially magnetized magnets to the pole pitch exist for both maximum force capability and minimum force ripple. The utility and accuracy of the analytical predictions and design optimization technique are demonstrated on a 9-slot/10-pole machine

Operator fidelity susceptibility: an indicator of quantum criticality

We introduce the operator fidelity and propose to use its susceptibility for characterizing the sensitivity of quantum systems to perturbations. Two typical models are addressed: one is the transverse Ising model exhibiting a quantum phase transition, and the other is the one dimensional Heisenberg spin chain with next-nearest-neighbor interactions, which has the degeneracy. It is revealed that the operator fidelity susceptibility is a good indicator of quantum criticality regardless of the system degeneracy.Comment: Four pages, two figure

Design of a miniature permanent-magnet generator and energy storage system

The paper describes a methodology for optimizing the design and performance of a miniature permanent-magnet generator and its associated energy storage system. It combines an analytical field model, a lumped reluctance equivalent magnetic circuit, and an equivalent electrical circuit. Its utility is demonstrated by means of a case study on a 15-mW, 6000-r/min generator, and the analysis techniques are validated by measurements on a prototype system

Spin-orbit field switching of magnetization in ferromagnetic films with perpendicular anisotropy

As an alternative to conventional magnetic field, the effective spin-orbit field in transition metals, derived from the Rashba field experienced by itinerant electrons confined in a spatial inversion asymmetric plane through the s-d exchange interaction, is proposed for the manipulation of magnetization. Magnetization switching in ferromagnetic thin films with perpendicular magnetocrystalline anisotropy can be achieved by current induced spin-orbit field, with small in-plane applied magnetic field. Spin-orbit field induced by current pulses as short as 10 ps can initiate ultrafast magnetization switching effectively, with experimentally achievable current densities. The whole switching process completes in about 100 ps.Comment: 4 pages, 3 figure