Remanence coercivity or remanent coercivity, typically denoted by H_c,r or H_r - a magnetic property of a magnetic material, characterising such a value of magnetic field strength H, which when applied and removed, leaves the given material in a state of zero net magnetisation, as measured by flux density B = 0, magnetic polarisation J = 0, or magnetisation M = 0. The remanence coercivity is measured by first driving the material under test to magnetic saturation, and then to remanence, as it is also typical for measuring ordinary coercivity.¹⁾²⁾³⁾

General procedure for measuring coercivity ⁴⁾

^{S. Zurek, E-Magnetica.pl, CC-BY-4.0}

Coercivity of magnetic materials is measured by using a measurement system appropriate for the type of material magnetic (soft, hard, semi-hard).⁵⁾ The particular procedures vary greatly, as dictated by the value of coercivity and the shape and size of the samples under test. However, from the conceptual magnetic viewpoint the procedure is similar in all cases, and can be broadly described as follows:

• Before the procedure, the material can be in any state of magnetisation (demagnetised, or magnetised, to any level, or in its remanence state).
• The first step (step 1 in the illustration) is to apply magnetic field which is high enough so that the state of magnetic saturation is obtained. The level of excitation is dictated by the type of material under test, and its expected value of coercivity. In any case, the applied saturating H must be much greater than the H_C to be measured, so at least H_sat > H_C but more accurately H_sat » H_C.
• After saturation, the excitation is reduced (step 2) to H = 0 (thus returning the material to the remanence point B_R = J_R, or M_R).
• Then a negative field is applied (step 3) progressively, so that the state of magnetisation begins to approach zero. The quantity of magnetisation (flux density B, polarisation J, or magnetisation M) is measured continuously during this phase. The value of H at which B, J, or M becomes zero represents the “ordinary” coercive field H_C for that value, namely _BH_C, _JH_C, or _MH_C.
• Measurement of remanence coercivity H_C,R is more complicated, because it can only be quantified after reducing the applied negative field back to zero (step 4) and checking if the remnant flux density, polarisation, or magnetisation is zero. If the curve does not return to (0,0) then the saturating procedure should be repeated and a different level of negative field needs to be applied, etc.⁶⁾
• Coercivity can be measured in both directions, for positive or negative applied field. The procedure is identical in both cases, but simply performed with the opposing magnetic polarity, or reversed position of the sample in the measurement system (and the value of H_C,R may be then averaged from both directions, for symmetrical materials).⁷⁾

Internal magnetic poles in a magnetic material ⁸⁾

^{S. Zurek, E-Magnetica.pl, CC-BY-4.0}

For most cases the point of remanence coercivity can be treated as synonymous with the point of full demagnetisation. However, under special conditions additional criteria has to be met, because local magnetisation can still persist, even if the global average of B = 0, J = 0, or M = 0. ⁹⁾

Therefore, it might be still required to apply alternating excitation with gradually reducing amplitude in order to achieve full demagnetisation of a given sample under test.

• Coercivity
• Remanence