Typically the coercivity of a magnetic material is determined by measurement of the magnetic hysteresis loop, also called the magnetization curve, as illustrated in the figure above. The apparatus used to acquire the data is typically a vibrating-sample or alternating-gradient magnetometer. The applied field where the data line crosses zero is the coercivity. If an antiferromagnet is present in the sample, the coercivities measured in increasing and decreasing fields may be unequal as a result of the exchange bias effect.