This book is a comprehensive text on the theory of the magnetic recording process. It gives the reader a fundamental, in-depth understanding of all the essential features of the writing and retrieval of information for both high density disk recording and tape recording. The material is timely because magnetic recording technology is currently undergoing rapid advancement in systems capacity and data rate. The competing technologies of longitudinal and perpendicular recording are given parallel treatments throughout this book. A simultaneous treatment of time and frequency response is given to facilitate assessment of signal processing schemes. In addition to covering basic issues, the author discusses key systems questions of non-linearities and overwrite. The emerging technology of magnetoresisitive heads is analysed separately and three chapters are devoted to various aspects of medium noise. This unique book will be valuable as a course text for both senior undergraduates and graduate students. It will also be of value to research and development scientists in the magnetic recording industry. The book includes a large number of homework problems.

[1] Hysteresis measurements have become an important part of characterizing magnetic behavior of rocks in paleomagnetic studies. Theoretical interpretation is often difficult owing to the complexity of mineral magnetism and published data sets demonstrate remanence and coercivity behavior that is currently unexplained. In the last decade, numerical micromagnetic modeling has been used to simulate magnetic particles. Such simulations reveal the existence of nonuniform remanent states between single and multidomain, known as the ''flower'' and ''vortex'' configurations. These suggest plausible explanations for many hysteresis measurements yet fall short of explaining high saturation remanence, high coercivity data such as those commonly observed in fine grained submarine basalts. In this paper, we review the theoretical and experimental progress to date in understanding hysteresis of geological materials. We extend numerical simulations to a greater variety of shapes and sizes, including random assemblages of particles and shapes more complex than simple rods and cubes. Our simulations provide plausible explanations for a wide range of hysteresis behavior.

A cubic discretization procedure of the micromagnetic energy functional is used to carry out numerical studies of the magnetization process in ferromagnetic cubes. Equilibrium magnetization configurations and their switching behavior are calculated for particle sizes in the range from 100 to 550 Å. In the model calculations the particles are assumed to have uniaxial crystalline anisotropy with an anisotropy constant of 18 500 erg/cm3, a saturation magnetization of 370 emu/cm3, and an exchange constant of 10−6 erg/cm. For particle sizes smaller than 520 Å the remanent state has a flowerlike magnetization configuration. Beyond 520 Å this state is replaced by a vortex structure about the easy axis. For particles smaller than 450 Å switching occurs by approximately uniform rotation of the flower state. The switching fields are larger than the corresponding Stoner–Wohlfarth value. Beyond 450 Å the application of an external field leads to the formation of a vortex configuration. The switching of the vortex configuration involves rotation of the vortex axis at a reduced value of the switching field. The angular dependence of the coercive field is calculated for particle sizes of 200, 400, and 550 Å.

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Anomalous metamagnetic-like transition in a FeRh/Fe3Pt interface occurring at T ≈ 120 K in the field-cooledcooling curves for low magnetic fields AIP Advances 2, 032168 (2012) Electric-field-control of magnetic anisotropy of Co0.6Fe0.2B0.2/oxide stacks using reduced voltage J. Appl. Phys. 112, 033919 (2012) Observation of intriguing exchange bias in BiFeO3 thin films J. Appl. Phys. 112, 033915 (2012) Rotary transportation of magnetic nanoparticle chains on magnetic thin film array A computer simulation model has been developed to conduct micromagnetic studies of thin magnetic films. Thin-film media are modeled as a planar hexagonal array of hexagonally shaped grains. Each grain is a single domain particle whose magnetization reverses by coherent rotation. The computation utilizes coupled gyromagnetic dynamic equations with phenomenological Landau-Lifshitz damping. In particular, the effects of particle interactions are investigated. The effect of media microstructure on magnetic hysteresis is examined a~ well as the effect of intergranular exchange coupling. The difference between planar and completely random orientation of the crystalline anisotropy axes is discussed. Recorded transitions are simulated by allowing a pair of perfect transitions to relax. With no intergranular exchange coupling, the transitions show profound irregularity and zig-zag structure. Intergranular exchange coupling produces more uniform transitions with increased zig-zag structure amplitude. For a closely spaced transition pair, the equilibrium configuration yields percolated transition boundaries with stable reverse island domains. The effect of gyromagnetic precession also has been examined.