Remanence is an essential property of materials. On the premise that self-demagnetization does not occur, the remanence of a magnet is constant, which is determined by the product raw material formula and preparation technology, and its test is carried out in a completely closed state.
Surface magnetism is the magnetic induction value of the measured location (a small area) when the magnet or magnetic component is in an open or semi-open state. The surface magnetic is a vector with direction. The surface magnetic data on different surfaces of the magnet varies greatly. We usually say that the surface magnetic value is perpendicular to the magnetic pole plane. The highest surface magnetic value of a single magnet is one half of the remanent magnetic value. Note that it is "single magnet". In some magnetic components and magnetic arrays, special magnetic circuit design can be used to improve the surface magnetic value of the magnet, and the value can even exceed the remanent magnetic value.
Magnetic flux is a measurement of the overall magnetic size of a magnet through coil testing. Usually magnetic components are not suitable for testing magnetic flux. Magnetic flux also has direction requirements by default. Of course, the total magnetic flux value can also be measured by using three-dimensional Helmholtz coil in actual measurement. Special attention should be paid to the testing direction when measuring surface magnetic flux and magnetic flux.
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If the magnetic path of the magnet is completely locked in a built-in space and no magnetism is displayed externally, then the magnet is in a closed-circuit state. The most typical one is the magnet under the demagnetization curve measurement, which almost does not show magnetism externally.
Above in addition to open and closed state, the rest can be called semi-open.
