Size dependence of the magnetic properties of electrochemically self-assembled Fe quantum dots

A quasi-periodic array of Fe quantum dots of cylindrical shape has been syn thesized by electrodeposition of Fe in porous alumina. By controlling the f abrication parameters, we have controlled the length, diameter, and spacing of the dots. The magnetic properties are shown to depend on these paramete rs. It has been found that at room temperature, there exists a critical dia meter of the dots for which the coercivity is a maximum. The largest value of coercivity obtained at room temperature is 2640 Oe which rises to 2900 O e an annealing. At a low temperature of 5K, an increase in coercivity is ob served for most of the samples. The largest value is 3800 Oe which rises to a value of 4100 Oe in the corresponding annealed counterpart. At 5K, no ma ximum is seen in the coercivity as a function of diameter. Instead, the coe rcivity is found to decrease with increasing diameter. This dependence of t he coercivity on diameter is discussed in terms of localized reversal effec ts.