Permanent Magnetic Polarity

8.09 Magnetic Polarity Reversals in the Core

(Matuyama–Brunhes), which occurred 0.78 Ma, the dating error of the most favorable basalt flows is comparable to the transition duration (Singer et al., 2005). For this reason transition duration must be obtained from sedimentary records, using the stratigraphic thicknesses of the transition zones and estimates of the deposition rate. From 30 selected records of the last four reversals, Clement...

Permanent magnets and hard magnetic materials

This review deals with the definition and development of hard magnetic materials with special emphasis on more recent developments in this field. After discussing the fundamental properties of all hard magnetic materials, based on the intrinsic and extrinsic properties, some remarks on the history of hard magnetic materials and permanent magnets are given. The important hard ferrites are only b...

A Novel Permanent Magnetic Angular Acceleration Sensor

Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating s...

Magnetic reversal in Sm2Fe17Ny permanent magnets

Reversal mechanism in permanent magnetic materials

The phenomenon of magnetization reversal in a hard magnet is studied analytically within a framework of a simplified energy minimization model for a two grain system. The transition region ~a domain wall-like moment structure! is found to play a crucial role in nucleating a reversed domain and in the subsequent formation of a domain wall near the grain boundary. This is shown to result in a con...