User:Schenad/退磁场
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退磁场(demagnetizing field),又称退磁磁场、反磁场或(磁体外的)杂散磁场(stray field),指的是磁体被磁化时产生的磁场(H场)。在某一包含有若干磁体的区域内,总磁场强度是这些磁体的退磁场加上自由电流(free currents)或位移電流所产生的磁场的总和。术语“退磁场”中的“退”反映了其作用于磁化强度以减小总磁矩的趋势。It gives rise to shape anisotropy in ferromagnets with a single magnetic domain and to magnetic domains in larger ferromagnets.
The demagnetizing field of an arbitrarily shaped object is very difficult to calculate even for the simple case of uniform magnetization. For the special case of ellipsoids (which includes spheres) the demagnetization field is linearly related to the magnetization by a geometry dependent constant called the demagnetizing factor. Since the magnetization of a sample at a given location depends on the total magnetic field at that point, the demagnetization factor must be used in order to accurately determine how a magnetic material responds to a magnetic field. (See magnetic hysteresis.)