Sweep rate dependence of coercivity in closed magnetic circuit

A hysteresisgraph has been set up to investigate the sweep rate dependence of coercivity on NdFeB magnets in closed magnetic circuit. The linear relationship between coercivity and logarithmic sweep rate has been found and the maximum difference of H_C in the sweep rate is 1.1%. The fluctuation field and activation volume have been deduced, which is in agreement with results in open magnetic circuit. This study is helpful to understand the coercivity variation of NdFeB in closed magnetic circuit in industrial measurement.