Today magnetic recording is still the leading technology for mass data storage. Its dominant role is being reinforced by the success of cloud computing, which requires storing and managing huge amounts of data on a multitude of servers. Nonetheless, the hard-disk storage industry is presently at a crossroads as the current magnetic recording techno

Application-oriented book on magnetic recording, focussing on the underlying physical mechanisms that play crucial roles in medium and transducer development for high areal density disk drives.

Patterned magnetic nano-structures are under extensive research due to their interesting emergent physics and promising applications in high-density magnetic data storage, through magnetic logic to bio-magnetic functionality. Bit-patterned media is an example of such structures which is a leading candidate to reach magnetic densities which cannot be achieved by conventional magnetic media. Patterned arrays of complex heterostructures such as exchange-coupled composites are studied in this thesis as a potential for next generation of magnetic recording media. Exchange-coupled composites have shown new functionality and performance advantages in magnetic recording and bit patterned media provide unique capability to implement such architectures. Due to unique resonant properties of such structures, their possible application in spin transfer torque memory and microwave assisted switching is also studied. This dissertation is divided into seven chapters. The first chapter covers the history of magnetic recording, the need to increase magnetic storage density, and the challenges in the field. The second chapter introduces basic concepts of magnetism. The third chapter explains the fabrication methods for thin films and various lithographic techniques that were used to pattern the devices under study for this thesis. The fourth chapter introduces the exchanged coupled system with the structure of [Co/Pd] / Fe / [Co/Pd], where the thickness of Fe is varied, and presents the magnetic properties of such structures using conventional magnetometers. The fifth chapter goes beyond what is learned in the fourth chapter and utilizes polarized neutron reflectometry to study the vertical exchange coupling and reversal mechanism in patterned structures with such structure. The sixth chapter explores the dynamic properties of the patterned samples, and their reversal mechanism under microwave field. The final chapter summarizes the results and describes the prospects for future applications of these structures.

The explosive increase in information and the miniaturization of electronic devices demand new recording technologies and materials that combine high density, fast response, long retention time and rewriting capability. As predicted, the current silicon-based computer circuits are reaching their physical limits. Further miniaturization of the electronic components and increase in data storage density are vital for the next generation of IT equipment such as ultra high-speed mobile computing, communication devices and sophisticated sensors. This original book presents a comprehensive introduction to the significant research achievements on high-density data storage from the aspects of recording mechanisms, materials and fabrication technologies, which are promising for overcoming the physical limits of current data storage systems. The book serves as an useful guide for the development of optimized materials, technologies and device structures for future information storage, and will lead readers to the fascinating world of information technology in the future.

In this dissertation thesis, I will discuss the fundamental basic technology necessary for continuing the prosperity status of 21 st century electronic devices; Lithography. I will give an overview of the concepts of scanning electron microscopy (SEM) and development of direct electron beam lithography (D-EBL) for magnetic bit patterned media (BPM), capable of achieving magnetic recording areal densities above 1 terabit/in [sperscript 2]. Furthermore, I will present the peripheral equipment mainly used for developing innovative processes.

The explosive increase in information and the miniaturization of electronic devices demand new recording technologies and materials that combine high density, fast response, long retention time and rewriting capability. As predicted, the current silicon-based computer circuits are reaching their physical limits. Further miniaturization of the electronic components and increase in data storage density are vital for the next generation of IT equipment such as ultra high-speed mobile computing, communication devices and sophisticated sensors. This original book presents a comprehensive introduction to the significant research achievements on high-density data storage from the aspects of recording mechanisms, materials and fabrication technologies, which are promising for overcoming the physical limits of current data storage systems. The book serves as an useful guide for the development of optimized materials, technologies and device structures for future information storage, and will lead readers to the fascinating world of information technology in the future.

Bit patterned media (BPM) have received increased attention in recent years as the primary candidate for 1 Terabit/in2 or higher recording density. A patterned media consists of an array of well-defined magnetic nanostructures, each of which can store one bit of data. In the simplest scheme, the structures could be magnetic pillars and dots with a single easy axis of magnetization. The direction of magnetization is interpreted as a binary 1 or 0. Some of the main technical issues in the BPM include the difficulty in fabricating small nano-island arrays in a periodic fashion over large areas, reliability/reproducibility of magnetic bit characteristics, wear and head flyability issue which is associated with the media surface roughness, and processing cost. This thesis deals with investigation of various fabrication approaches, nanostructural features, and magnetic properties for the bit patterned media. In Chapter 1, the science and technology of patterned magnetic recording media are discussed. In Chapter 2, fabrication of an array of high-coercivity magnetic Co/Pd multilayered islands using pre-patterned Si nanopillars template is described. The Si nanopillars have been prepared by advanced electron beam lithography (EBL) and reactive ion etching (RIE). In Chapter 3, the flying instability of the read/write recording head-slider on the topographically rough surfaces of the nano-patterned media is discussed, and technical approaches to overcome such a problem is described, such as planarization of nanopatterned topography by refilling the trenches and flatten the surface of the BPM. I have investigated the head flyability on BPM by fabricating nano pillar geometry with different topography. For flyability testing that requires a relatively large area, I have also fabricated nano pillars on 2.5 inch glass disks with a distribution of pillar size and periodicity using the "silver ball-up process" and RIE. The process, structure and properties of planarized vs. non-planarized nano fabricated and imprinted BPM, are described in Chapter 4. A Si substrate was spin-coated with a thin PMMA layer, and a periodic island array was made by nano-imprinting lithography (NIL) with the patterned nanofeatures. The subsequent pattern transfer to the Si substrate was performed by using RIE process. A Co/Pd multilayer film was sputtered on the pre-patterned substrate. A HSQ layer was first spin coated on the patterned media to fill the trenches and subsequently re-etched by RIE to remove the overfilled regions on the substrate for planarization. In Chapter 5, the effect of magnetic island geometry on switching field distribution is discussed.