Enhanced Coercivity in Submicrometer-Sized Ultrathin Epitaxial Dots with In-Plane Magnetization

We present measurements, analysis, and modeling of magnetization reversal processes in ultrathin magnetic dots with in-plane magnetization. This study is performed on a model system: Arrays of tens of millions of epitaxial (110) Fe dots. We clearly demonstrate the link existing between the increase of dot thickness and the decrease of reversal field as compared to coherent rotation (CR) predictions. For 1-nm-thick films $H_r\left(\theta \right)$ is very close to CR law, although magnetic relaxation experiments clearly show that nucleation volumes are by far smaller than an individual dot volume. This apparent discrepancy is discussed. An analytical model is proposed to describe magnetization reversal in this kind of dots.