Magnetism is a natural phenomenon that can be observed. This article includes how the magnetism used to make data storage devises. Data storing not electronics at all. It is a complete property of the materials. Engineers are usually concerned only with ferromagnetic materials and need to know the total flux density B (B-internal magnetic field) produced by a given field H (H-external magnetic field). they therefore often find the B.H curve also called a magnetization curve more useful than the M, H curve. Iron (Fe), Nickel (Ni), Cobalt (Co), Gadolinium (Gd) are ferromagnetic materials at room temperature.

These materials are divided into small regions called magnetic domains; the boundary separating them called domain walls. The magnetic alignment of those domains are totally random and therefore naturally materials are neutralized. But when we applied an external magnetic field into the materials, those domains tend to rotate and align to the external fields. However, these magnetic forces have to overcome the thermal vibrations as well. This leads to having permanent magnets.

Before archive that, there is an intermediate situation as well this process can reversible. If all domains align to the external forces, they won’t able to come back to their original positions. For that, there should have an opposite magnetic field. These differences made a hysteresis loop.

  1. Neutral material: No external and internal magnetic fields
  2. Material magnetized positively: There are external and internal magnetic fields (Maximum level)
  3. Remaining internal Magnetic field: External field is zero
  4. Material neutralized: There is a negative external magnetic field
  5. Material magnetized negatively: There are external and internal magnetic fields (Maximum level)
  6. Remaining internal Magnetic field: External field is zero
  7. Material neutralized: There is a positive external magnetic field

These remaining magnetic field can be used as electronic memorization for 1 and 0. Once the external force applied there are remaining that field although remove that external force. If it is taken as 1, that can be read again. Old gramophone disks, music tapes, hard disks are working based on this principle. They use electromagnetic coil for reading and recording both.



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