图。1
所有铁磁材料都具有原子磁矩，其在称为结构域的小区域中彼此平行对齐。在这些结构域内，存在的自发磁化等于材料的饱和磁化强度，因此各个域始终完全磁化。在没有施加的场的情况下，由于每个域的磁化方向是随机定向的，因此没有由材料产生的净磁矩或场。
During magnetization of the material, domains whose magnetization directions have a component in the direction of the applied field will grow at the expense of those that do not. Once all of the unfavorably oriented domains have been eliminated by domain wall movement, the magnetization direction of the single domain that remains will be rotated to be parallel to that of the applied field (see figure 1).
图2
During magnetization, an increasing magnetic field is applied to the material until a saturation point is reached. Upon removing this applied field, a permanent magnet material will not follow the same path down to flux density = 0, instead, it will retain some of its magnetism. The path that the permanent magnet follows is called a hysteresis loop and is a key tool in the quantitative analysis of permanent magnet performance.
这些环是施加的磁场与所得诱导磁化在材料内的关系的图形表示。由现在磁化材料产生的字段（B.一世）添加到应用领域的（H）被称为正常诱导（B.N) or simplyB.。Since this induction has two components, it is defined as:
B.= B一世+ H
这B和H curve is known as the normal curve, while theB.一世vs H曲线称为内在曲线。这些曲线的示例，也称为滞后环，如图2所示。环路显示磁性材料的性质，因为它被磁化和脱磁。随着磁体执行工作，循环的第二象限显示磁性。通过将第二象限与给定磁路内的已知参数进行比较，可以确定磁输出的近似。
When a magnetic field is applied to unmagnitized material, the intrinsic induction (B.一世）在其内建立，平行于所施加的领域。如果H一世s sufficiently strong, the magnet will become fully magnetized at the saturation flux density (B.sat）。当场降至零时，磁铁将反冲到残余值或剩余（B.R.），只要磁铁在闭合磁路内。与软磁材料不同，不存在外部磁场不会导致退磁。
图3.
One or more air gaps introduced into a magnetic circuit will enable useful work to be performed. The mechanical energy used to separate a magnet from soft iron is stored as potential energy within the air gap and the magnet. This moves the point of operation on the intrinsic curve to the second quadrant. The normal curve in the second quadrant represents the energy output of the magnet and is used during magnet design. If the iron in the circuit is completely removed, the air gap becomes very large and the operating point of the curve now approachesHC.一世N这second quadrant (known as normal coercivity) and the induction (B.) will approach zero.
如果这air gap is closed again, the stored potential energy is used to perform the work of bringing the magnet and the iron together. The operating point does not, however, return toB.R.。磁铁沿着所谓的次要滞后循环循环到下面的一个点B.R.（图3.）。Repeated opening and closing of the air gap will result in the magnet cycling along this minor hysteresis loop. The average slope of the minor hysteresis loop is the recoil permeability (
如果退磁领域的增加超过HC, the operating point of the magnet now moves into the third quadrant of the normal curve. Ultimately, when the intrinsic coercivity (HCI.) is reached, the magnet is completely demagnetized. this value is a measure of the magnet's ability to resist demagnetization.
Anisotropy in a material is observed when the properties of that material differ depending on its orientation and the direction of testing within the material. In permanent magnets, spontaneous magnetization within domains occurs along certain axes within the material, corresponding to the crystal structure or crystallography of the material. Atomic magnetic moments will align themselves in these directions.
这种取向称为磁镀晶各向异性，是现代永磁体如NDFEB高性能的关键因素之一。当在材料内没有优选的晶形方向时，如果材料内存在非球形颗粒，则可能出现形状各向异性。这种颗粒的长轴存在于材料内。这种颗粒的长轴将是优选的磁轴。Alnico磁铁家族是具有这种类型各向异性的材料的一个例子。与永磁体相关的其他显着各向异性是由于在材料内作用的应力而发生的。当沿特定方向施加拉伸或压缩应力在永磁体上时，将材料沿着该方向磁化到永磁体上。
Magnet geometry is another factor in how difficult it is to magnetize and demagnetize. A magnet with a geometry that causes it to work on a load line below the knee of its second quadrant demagnetization curve will not retain all of the flux that the material is capable of handling, so it will not provide full potential energy to a magnetic circuit. This can be overcome by magnetizing a magnet in its final circuit configuration, i.e. with steel components, or by stacking several magnets together while magnetizing.
为了达到饱和，磁铁应暴露于大于其总和的磁化区域HCI.价值加上H从绘制负载线斜率绘制的值B.R.point to the positiveH轴。叠加磁铁增加载重线slope which reduces the magnetizing force required.
In general, magnet materials respond negatively to heat because thermal energy reduces the flux density and the ability of domains to remain aligned. Increased thermal energy increases the disorder present and at a particular temperature, the Curie point, the material will lose its ferromagnetism. Overheating a magnet may cause metallurgical changes to occur; in many magnets the safe operating temperature will be less than the Curie point. The one exception are the ferrites (ceramic magnets), which, due to their chemical nature, can withstand temperatures significantly past their Curie points. The ferrites also exhibit the unusual characteristic of an increased coercivity with temperature. Heat treatments as part of the magnet manufacturing process are precisely calculated to precipitate desired phases and to control metallurgical changes.
永磁材料有时掺杂有其他元素，以抑制畴壁运动。然而，这通常伴随着产生的通量量的相应减少，因为这些元件减少了材料内的硬磁相体积。
Post magnetizing treatments like stabilizing, calibrating and thermal cycling all have the same effect on magnets- they provide external energy to allow weak magnetic domains to reverse. After treatment, the magnet is stable until some greater level of external energy is added to the system. Thermal cycling adds random energy to the magnet, and its effect depends on the magnet's so-called self-demagnetizing field. this field is the result of external flow of magnetic flux from one pole back to the other, as well as flux that returns at sub-surface levels. The self-demagnetizing field is affected primarily by the magnet's geometry.
Stabilizing a magnet is a process that uses a reverse magnetic field to do the same thing as temperature cycling. Both stabilizing and thermal cycling result in 'knocking down' of the magnet by some degree. Calibrating, on the other hand, is the process of reducing the magnitude of the magnetic moment of each component so that all magnets act the same in the magnetic circuit.
在需要后磁化处理的所有情况下，应考虑操作磁路中的有效载荷线。如果磁体通过其自身循环而不会影响其他相关电路部件的影响，则效果将与电路中的温度循环不同。如果要独立于其他部件处理磁体，则应确定并指定操作负载线，以便在操作条件下进行处理。
