Temperature Dependence of Coercivity Behavior in Fe Films on Fractal Rough Ceramics Surfaces

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In this paper we study the anomalous magnetic properties in Fe films on fractal rough \alpha-Al2O3 ceramics surfaces. It is found that the temperature dependence of the coercivity H_{\text{c}} of the Fe films exhibits a peak around a critical temperature T_{\text{crit}} = 10 K: firstly, H_{\text{c}} increases with the temperature T; then it decreases rapidly as T further increases. The peak of the coercivity goes up with the decrease of the film thickness. It is estimated that, for T < T_{\text{crit}}, the anomalous coercivity behavior may be resulted from the coupling effect of the spin-glass like states and ferromagnetic phases, for T > T_{\text{crit}}, the observed coercivity behavior is mainly dominated by the effect of the non-uniform size distribution of the single-domain particles or magnetic clusters. The study shows that the enhancement H_{\text{c}} of the Fe films is strong related to the roughness of the film surfaces induced by the fractal ceramics surfaces. The results are further confirmed by the thermoremanence and vibrating sample magnetometer measurements.
2013-01-25