Fabrication, characterization, and micromagnetic analysis of lithographically defined particle arrays for applications in data storage

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001.Includes bibliographical references (leaves 101-103).In this thesis, the magnetic behavior of nanostructured ferromagnetic particle arrays are studied by experiments and numerical micromagnetics for ultra-high-density data storage applications. 1 00nm or 200nm period arrays of nanostructured nickel, cobalt, and cobalt phosphorus are fabricated by the techniques of interference lithography combined with evaporation and electrodeposition. The nanomagnet arrays are characterized by bulk magnetometry and magnetic force microscopy. The remanent states of evaporated conical particles and electrodeposited cylindrical particles are studied by micromagnetic simulations and compared with experimental measurements. For electrodeposited particles, the influence of size, aspect ratio and microstructure on switching field is also investigated. Finally, the effect of demagnetizing magnetostatic interactions and switching field spread on the squareness and the shape of hysteresis loops is studied with the help of an Ising-like interaction model. Based on these observations, a stability condition for patterned media is found and used for determining the optimum spacing between nanomagnets.by Minha Hwang.Ph.D