The efficiency and the demagnetization field of a general Halbach cylinder

Abstract

The maximum magnetic efficiency of a general multipole Halbach cylinder of order $p$ is found as function of $p$. The efficiency is shown to decrease for increasing absolute value of $p$. The optimal ratio between the inner and outer radius, i.e. the ratio resulting in the most efficient design, is also found as function of $p$ and is shown to tend towards smaller and smaller magnet sizes. Finally, the demagnetizing field in a general $p$-Halbach cylinder is calculated, and it is shown that demagnetization is largest either at $\cos 2p\varphi =1$ or $\cos 2p\varphi =-1$. For the common case of a $p=1$ Halbach cylinder the maximum values of the demagnetizing field is either at $\varphi =0,\pi$ at the outer radius, where the field is always equal to the remanence, or at $\varphi =\pm \pi /2$ at the inner radius, where it is the magnitude of the field in the bore. Thus to avoid demagnetization the coercivity of the magnets must be larger than these values.

arXiv comment5 pages, 5 figures

References in corpus (4)

• Review and comparison of magnet designs for magnetic refrigeration
• Optimization and improvement of Halbach cylinder design
• Analysis of the magnetic field, force, and torque for two-dimensional Halbach cylinders
• The ideal dimensions of a Halbach cylinder of finite length

Cited by in corpus (5)

• Practical Concepts for Design, Construction and Application of Halbach Magnets in Magnetic Resonance
• Topology optimized permanent magnet systems
• A topology optimized switchable permanent magnet system
• Metamaterial anisotropic flux concentrators and magnetic arrays
• The magnetic properties of the hollow cylindrical ideal remanence magnet