Magnetization reversal in lithographically patterned sub-200-nm Co particle arrays

A series of Co particle arrays with rectangular elements having a thickness of 10 nm, a width of 90 nm and aspect ratios of 1.3, 2.2, and 3.3, has been fabricated using interference lithography. The switching behavior of these arrays has been studied by measuring isothermal remanence measurement (IRM), dc demagnetization measurement (DCD), and hysteresis loops using magnetometry and magnetic force microscopy (MFM). The single domain structure is the only stable structure at remanence. Nonuniformity and redeposition debris from ion beam etching (IBE) cause a large reversible magnetization component. The comparison between IRM and DVD curves shows that the interactions between the dots are negligible. Both vibrating sample magnetometer (VSM) measurements and MFM images show that the dots switch over a large range of fields, which is believed due mainly to the crystallographic orientation distribution of the grams within each element.