Dependence of nucleation fields of MnBi films on film thickness

Hysteresis loops of thin MnBi films on mica and on glass show that a relationship exists between film thickness and nucleation field. Generally, It appears to be impossible to calculate nucleatlon fields of magnetic materials since these fields depend on materials imperfections which introduce unknown free energy contributions. The present work shows that for MnBi films a theory can be developed with which the nucleation fields can be calculated. Measurements of the nucleation fields Hnand calculated values are in good agreement with each other.