In varying degrees, all substances are magnetic, however, those who belong to the class of ferromagnetic materials, with its own structure, which allows to keep directional field.This quality is widely used for the information recording layers on the surface of which can be oriented by creating a "storage".During magnetization used a physical phenomenon that can be described by the word "lag".Graphically, it shows the so-called hysteresis loop.
ferromagnets have the ability to spontaneously magnetized in their molecular structure are present domains, that is, the centers of the magnetization, however, omni directional lines of force offsetting their effects and, therefore, a piece of conventional iron or nickel intrinsic magnetic field is created.
order to become ferromagnetic magnet, the magnetic field domains need to tilt in one direction, for which they must be subjected to an external field action, in which is manifested the hysteresis loop.
increase in the intensity of the magnetic field around the ferromagnet leads to an orientation previously chaotic domain, and create their own direction of the field, with a plot of these two parameters is the top point of saturation, in which the material becomes single-domain.When you create a field, you can reverse the lower reach saturation point, but the line chart will not repeat his direct running, and will be set back, as to reorient domains require additional energy.The hysteresis loop - a loop graphically expressed ambiguity strength values relative induction in forward and reverse directions.
Actually, many mechanical processes are also characterized by a delay associated with the impact of a change in direction is reversed.For example, when the elastic deformation of the body and change its size is ambiguous, and their charts - the same hysteresis loop.The inertia inherent in any physical processes.
properties of ferromagnets retain its magnetization is the basis of the principle of magnetic recording.
The first tape recorders as a carrier used steel wire which passed the recording head, which is a coil magnetized depending on the intensity of the field generated by it.Then, with the improvement of equipment, began to use the tape coated with a layer of powder material having higher magnetic properties, however, the general principle remains the same.Ferromagnetic hysteresis loop creates conditions for the preservation of recorded information on this material.
Household recorders nowadays hardly used, however, this does not mean that the principle of their work has lost its meaning.In modern computers to store information on hard disks used the same principle of magnetic recording, which is based on the hysteresis loop.
