The phenomenon causing the values of the magnetic flux density to lag behind the values of the magnetizing force so that the increasing and decreasing fields differ in magnitude. In regard to YIG-Tuned oscillators, a magnetic lag effect of the magnetic components of a YIG device that occurs when the tuning coil current is changed. Hysteresis is measured in terms of the maximum resulting frequency difference at a particular magnet current when the device is turned from high to low frequency range.