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The leading magnetic material for use in data recording tapes is the metal particulate (MP) composition. The trend to smaller particle size necessarily entails an increase in thermally induced time effects. An Arrhenins-Neel switching model is used, together with the dependence of the experimental coercivity on field duration, to determine an effective switching volume. The model takes account of the highly imperfect magnetic orientation present in actual recording media. Results for coated media made with current advanced particles having various degrees of orientation (squareness) show that the calculated switching volume is not sensitive to orientation above a squareness value of about 0.6 (essentially random in plane). This switching volume correlates well with particle volume, as determined by transmission electron microscopy (TEM). These results confirm the practical relevance of the model, both for realistic tapes and for disks that have random grain orientation, and are evidence that the model adequately takes account of preferred-axis misalignment. Index Terms--Coercivity, magnetic recording, magnetic stability, magnetic tape, metal particles, metal particulate (MP), superparamagnetism, thermal stability, time effects.

Here we demonstrate optical pumping of a single electron within a semiconductor nanostructure comprised of a single fluorine donor located within a ZnSe/ZnMgSe quantum well. Experiments were performed to detect optical pumping behavior by observing single photons emitted from the nanostructure when the electron changes spin state. These results demonstrate initialization and read-out of the electron spin qubit and open the door for coherent optical manipulation of a spin by taking advantage of an unconventional nanostructure.