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Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization.The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ.
The magnetomechanical effect is a fundamental feature of ferromagnetism. The fact that the application of external stresses alters the flux density of a magnetized ferromagnet, and thus the shape, and size of its hysteresis loops is easily changeable.
However, coupling between the magnetization and the lattice does result in deformation, an effect called magnetostriction. To keep the lattice from deforming, a stress must be applied. If the crystal is not under stress, magnetostriction alters the effective magnetocrystalline anisotropy.
E λ is magnetoelastic anisotropy energy: This energy is due to the effect of magnetostriction, a slight change in the dimensions of the crystal when magnetized. This causes elastic strains in the lattice, and the direction of magnetization that minimizes these strain energies will be favored.
Magnetostriction forces are concentrated inside the ferromagnetic material itself. Lorentz or Laplace forces act on conductors plunged in an external magnetic field. Equivalent electromagnetic forces due to the presence of an electrical field can involve electrostatic , electrostrictive and reverse piezoelectric effects.
The magnetostriction characterizes the shape change of a ferromagnetic material during magnetization, whereas the inverse magnetostrictive effect characterizes the change of sample magnetization (for given magnetizing field strength ) when mechanical stresses are applied to the sample.
Strip of permalloy. Permalloy is a nickel–iron magnetic alloy, with about 80% nickel and 20% iron content.Invented in 1914 by physicist Gustav Elmen at Bell Telephone Laboratories, [1] it is notable for its very high magnetic permeability, which makes it useful as a magnetic core material in electrical and electronic equipment, and also in magnetic shielding to block magnetic fields.
Magnetoresistance is the tendency of a material (often ferromagnetic) to change the value of its electrical resistance in an externally-applied magnetic field.There are a variety of effects that can be called magnetoresistance.