Isolated and interactive arrays of magnetic nanostructures as small as 15 nm are fabricated using nanolithography and related technologies, and are characterized using magnetic force microscopy. It has been demonstrated that manipulating the size, aspect ratio, and spacing of these nanostructures can lead to unique control of their magnetic properties. A quantum magnetic disk based on discrete single-domain nanomagnetic structures with storage density of 65 Gbits/in. 2 is demonstrated along with a low-cost method for mass producing such disks. Other impacts that nanofabrication can bring to the development of future magnetic storage are discussed.

Metal rings with inner diameters of 1 and 5 m, fabricated using electron-beam lithography, were used to calibrate magnetic force microscopy ͑MFM͒. A MFM tip's effective magnetic charge, q, and effective magnetic moment along the tip's long axis, m z , can be determined from the MFM signal of the ring at a different scan height and a different electric current in the ring. The magnetic moments in the directions transverse to the tip's long axis were estimated by a straight current wire. It was found that for a Si tip coated with 65 nm cobalt on one side, q is 2.8ϫ10 Ϫ6 emu/cm, m z is 3.8ϫ10 Ϫ9 emu, and m x and m y are in the order of 10 Ϫ13 emu, which are negligible compared with m z. Furthermore, the MFMs sensitivity to the second derivative of the magnetic field was determined from the minimum ring current for a measurable MFM signal to be 0.1 Oe/nm 2 .

The switching behavior of isolated nanoscale nickel and cobalt bars, which were fabricated using electron-beam lithography, was studied as a function of bar length. The bars have a 35 nm thickness, a 100 nm width, and a length varying from 200 nm to 5 m. Magnetic force microscopy showed that except for the Ni bars with a length equal to or less than 250 nm, all other as-fabricated bars were single domain. Unlike the bar width dependence, the switching field of the single-domain bars was found to first increase with the bar length, then decrease after reaching a peak. The peak switching field and the corresponding bar length are 640 Oe and 1 m for Ni and 1250 Oe and 2 m for Co, respectively. The nonmonotonic length dependence suggests that the magnetization switching may be quasicoherent in the short bars and incoherent in the long bars, and that the exchange coupling is much stronger in Co bars than in Ni bars. Furthermore, the switching field of 1-m-long Co bars was found to increase monotonically as the bar width decreases, reaching 3000 Oe at a 30 nm width.

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Metal rings with inner diameters of 1 and 5 m, fabricated using electron-beam lithography, were used to calibrate magnetic force microscopy ͑MFM͒. A MFM tip's effective magnetic charge, q, and effective magnetic moment along the tip long axis, m z , can be determined by the current flowing in the ring. The magnetic moments in the directions transverse to the tip's long axis were estimated by a straight current wire. It was found that for a silicon tip coated with 65 nm thick cobalt on the side, q ϭ 2.8 ϫ 10 Ϫ6 emu/cm, m z ϭ 3.8 ϫ 10 Ϫ9 emu, and m x ϭ m y ϭ 10 Ϫ13 emu, which are negligible compared with m z. Furthermore, the tip's sensitivity to the second derivative of the magnetic field was found to be about 0.1 Oe/nm 2 .