Orientation dependence of the dynamic coercivity of Stoner-Wohlfarth particles

The time dependence of the remanent coercivity for noninteracting Stoner-Wohlfarth particles with uniaxial anisotropy has been calculated numerically as a function of easy axis angle and distribution width. The results have been interpreted in terms of a simplified effective energy barrier function of the form ΔE=CKV(1-H/H₀)ⁿ and a modified Sharrock equation. For a system with identical easy axis angles, Sharrock law behavior occurs at all angles over a wide range of times with C=1 and n a function of angle. For a distribution of easy axes, Sharrock law behavior also occurs with C=1 and n≈1.5 for squareness values ranging from random to at least 0.98. The dependence of the energy barrier on field and easy axis angle is compared with the Victora expansion and with the Pfeiffer model