Some Magnetic Recording Developments

Abstract

Magnetic recording has been for some time one of those areas of engineering that managed to capture many researchers’ attention, and ultimately their imagination. One always seems to wonder how far we can still go in the pursuit of higher recording densities, and what kind of limitations are threatening to put an end to our magnetic storage dreams. Thus, we cannot leave this introduction to magnetism and magnetic materials without discussing some new developments in magnetic thin film systems, or improvements in writing/reading capabilities of magnetic devices that serve them. Additionally, we should also have a look at reasons behind some technological challenges encountered in the pursuit of higher recording densities. A few are mechanical, as they relate directly to the flying height of heads on the hard drive or contamination sensitivity issues. Others are problems inherent to the media, such as noise and data stability. Nevertheless, in spite of numerous obstacles, the magnetic recording industry somehow manages to push further its technological limits, ultimately overcoming numerous hurdles. Fortunately, the human mind has proven to be an endless source of innovation, and will likely find answers to many problems still awaiting to be unveiled.The multilayer spin valve GMR sensors and the unique MTJ-based devices presented in previous chapters were once a curious novelty in spintronic technologies. Nevertheless, they are nowadays absolutely essential for further developments in magnetic recording. Furthermore, we have seen that through their design, spintronic devices rely on the flow of spin-polarized electrons, usually manipulated with the use of magnetic fields. However, magnetic fields are also needed to control the orientation of magnetic moments in magnetically engineered thin film systems. These are part of the magnetic hard disk drive, allowing magnetic storage and retrieval. Unfortunately, shape-dependent demagnetizing fields in micro and nanoscale magnetic structures raise the necessity of increasing the magnetic fields required to change the magnetic state of sensor devices. This means that sensors will be limited in what strengths of magnetic fields they can detect, as the low fields between transitions would become in this case undetectable. Consequently, demagnetizing fields and the control over them play a significant role in designing good sensors. Moreover, as areal densities increase and bit size correspondingly decreases, we cannot but ask ourselves how much more information can we store and extract from the ever decreasing volume of our magnetic media? We keep thus stumbling across added barriers that are putting at risk further developments in magnetic information storage.Magnetic recording has evolved over a long and uneven road since the middle of the last century, with a few significant milestones along the way. From the economical magnetic tapes with their reduced per-bit cost and high reliability to the magnetically engineered nanostructures of the twenty-first century, this industry has known its ups and downs through numerous challenges. Many new developments would not be possible without advances in nanofabrication on which magnetic electronics have come to rely so heavily. Therefore, in this chapter, we will be reviewing some of these design and fabrication questions and solutions, in particular those related to the magnetic media themselves. We will finally end by having a look at new trends in magnetic memory types such as high-performance nonvolatile magnetic random access memories. As these open new doors for data storage, they arrive with an entire set of specifically new and sometimes unpredictable challenges waiting to be embarked upon.