From its inception until today, and for the foreseeable future, magnetic data storage on disks and tape has provided constantly increased storage density.This has required not only constant innovation, but also major breakthroughs in magnetic materials, both for the media and the read head. Today's disk and tape drives take advantage of novel nanoengineered composite magnetic materials and quantum mechanical processes.In this issue of MRS Bulletin, we present a number of review articles by some of the leaders in this rapidly moving field that highlight the key materials science accomplishments that have enabled the tremendous progress in hard disk drive and magnetic tape technologies.Individual articles describe the materials involved in state-of-the-art magnetic recording, advanced media for perpendicular magnetic recording, the materials challenges of achieving high performance in flexible media such as magnetic tape, the materials issues of read heads, and future avenues for magnetic storage beyond magnetic recording, such as nanowires and spintronics.

Magnetic recording has progressed dramatically over the last 50 years, with an increase of almost eight orders of magnitude in the amount of information stored per unit area of disk space.Two key enablers of this progress have been the recording medium and the read-back head.This article reviews the current state of the art in multilayer thin-film longitudinal recording media and giant magnetoresistive (GMR) read heads, with particular emphasis on the nanostructured magnetic materials that are key to today's high-performance hard disk drives.

The requirements for media for high-density magnetic recording are reviewed, particularly with respect to the emerging technology of perpendicular magnetic recording.It is discussed in general how suitable properties of the recording films can be achieved in practice.Several approaches to extend the thermal limit of magnetic recording technology are outlined.

Spin-polarized currents can be generated by spin-dependent diffusive scattering in magnetic thin-film structures or by spin-dependent tunneling across ultrathin dielectrics sandwiched between magnetic electrodes.By manipulating the magnetic moments of the magnetic components of these spintronic materials, their resistance can be significantly changed, allowing the development of highly sensitive magnetic-field detectors or advanced magnetic memory storage elements.Whereas the magneto-resistance of useful devices based on spin-dependent diffusive scattering has hardly changed since its discovery nearly two decades ago, in the past five years there has been a remarkably rapid development in both the basic understanding of spin-dependent tunneling and the magnitude of useful tunnel magnetoresistance values.In particular, it is now evident that the magnitude of the spin polarization of tunneling currents in magnetic tunnel junctions not only is related to the spin-dependent electronic structure of the ferromagnetic electrodes but also is considerably influenced by the properties of the tunnel barrier and its interfaces with the magnetic electrodes.Whereas the maximum tunnel magnetoresistance of devices using amorphous alumina tunnel barriers and 3d transition-metal alloy ferromagnetic electrodes is about 70% at room temperature, using crystalline MgO tunnel barriers in otherwise the same structures gives tunnel magnetoresistance values of more than 350% at room temperature.

For many decades, it was assumed that the characteristics of magnetic domain walls were determined by material properties and the walls were moved by magnetic fields.In the past few years, it has been shown that domain walls behave differently on the nanometer scale.Domain walls in small elements exhibit complex spin arrangements that strongly deviate from the wall types commonly encountered in magnetic thin-film systems, and they can be modified by changing the geometry of the element.Domain walls in nanowires can also be moved by injecting electrical current pulses.Whereas wall propagation is qualitatively explained by a spin transfer from the conduction electrons to the spins of the domain wall, important aspects of the observations cannot be explained by present models.Examples include the observation of a drastic transformation of the wall structure upon current injection and domain wall velocities that tend to be orders of magnitude smaller than anticipated from theory.

Reasearch and technology developments in the field of spintronics have grown tremendously in the past 10-15 years and already have had a major impact on the data storage industry.The future looks even brighter, as many new spintronic discoveries have been recently made that promise an even bigger impact in the future.This article summarizes the past accomplishments, describes some of the major discoveries that will have a lasting impact on the field, and discusses some of the technologies that may revolutionize data storage in the next decade.

By the end of 2006, the areal density of magnetic recording on tape will approach that seen in hard disk drives of the early to mid-1990s.These operating conditions are reviewed in relation to the operating conditions deemed necessary for the future of magnetic data storage on tape.What results is a clear set of tasks, encompassing both materials and systems architecture issues, to achieve very high-density data storage on magnetic tape, leading to 10 Tbyte tape cartridge capacities and higher.The key to achieving on tape the areal densities of tens to hundreds of Gbit in.2, common in hard disk drives (HDDs), lies primarily in the properties of the medium itself.As for volumetric density of the storage entity, HDDs and tape cartridges are roughly equivalent.The mechanical dimensional uncertainties that accompany the use of flexible, as opposed to rigid, media means that both the mechanical and magnetic properties of materials play a key role in the future of tape.The need for new architectures to overcome the track placement problem that results from increasing track density on flexible media are reviewed, as well as the “particles in a binder” concept that has served so well as the physical basis of tape media over the past 50 years.

The broader context of this discussion, based on a workshop where materials technologists and computational scientists engaged in a dialogue, is an awareness that modeling and simulation techniques and computational capabilities may have matured sufficiently to provide heretofore unavailable insights into the complex microstructural evolution of materials in extreme environments.As an example, this article examines the study of ultrahigh-temperature oxidation-resistant ceramics, through the combination of atomistic simulation and selected experiments.We describe a strategy to investigate oxygen transport through a multi-oxide scale—the protective layer of ultrahigh-temperature ceramic composites ZrB2-SiC and HfB2-SiC—by combining first-principles and atomistic modeling and simulation with selected experiments.