Thousands of products in stock
Weiß' districts
In magnetism, Weiß' areas (or Weiß areas) are delimited areas with the same polarization. They appear as microscopic, magnetized domains in the crystals of a ferromagnetic substance. They got their name from their discoverer Pierre-Ernest Weiss, a French physicist who spent his life extensively studying magnetic phenomena.
Explanation of the Weiss districts
Ferromagnetic substances such as iron consist of a number of small elementary magnets that have a uniform direction of magnetization within a domain (Weissian domain). Weiss had this knowledge in 1907 when he investigated the magnetic moments of atoms. The Weiß domains are separated from each other by so-called Bloch walls (magnetization transitions between the Weiß domains). In the case of non-magnetic materials, the Weiss domains are magnetically disordered and thus behave neutrally towards the outside.
The orientation of the Weiss domains (magnetized by nature to saturation) is based on the crystal lattice of the material. If an increasing magnetic field is brought close to the material, the Bloch walls of those Weiss domains that are already pointing in the direction of the external magnetic field shift first. If the external field is further strengthened, the other domains also change their polarity and merge with one another.
Is it possible to make Weiß' districts visible?
The Weiss domains could be made visible in physics by several methods:
With the help of a macroscopic model one can recognize the orientation of the Weiß' districts. To do this, a rotating set of compass needles is placed on a surface. If the needles come too close, they are influenced by the neighboring magnetic fields and align themselves parallel. This effect can be accelerated by the influence of temperature or vibration.
The Bloch walls, of course, only become visible at the microscopic level. Ferromagnetic particles such as iron dust are positioned on another ferromagnetic material. Thanks to the magnetic properties, the dust aligns with certain areas, the Bloch walls of the Weiß' districts.
The moment of polarity reversal can also be audible. To do this, the gradual increase in the magnetic field must be inductively picked up and amplified with a coil. With every change in the external field, noise can be heard due to the hysteresis of the Weiß' districts, which makes it possible to describe the properties of the ferromagnetic material.
The Weiß' districts play an important role in ferromagnetism. Even if the field strength vanishes (e.g. if the coil has no current), a certain remanence remains, which means that the material acts like a permanent magnet . Weiß' districts are used especially in storage processes, for example in magnetic tapes, magnetic disks or floppy disks.