N anomagnetism, the scientific field dedicated to the study of nanoscale magnetic objects, has undergone an explosion of activity over the last few decades, driven by fascinating discoveries such as the interaction of magnetization with spin currents (the area of spintronics)1,2 and a wide range of real-world applications3–7. For example, since both the storage and sensing parts of hard disk dr...

Starting from the second equilibrium equation in the BBGKY hierarchy under the Kirkwood superposition closure, we implement a new method for studying the asymptotic decay of correlations in the hard disk fluid in the high density regime. From our analysis and complementary numerical studies, we find that exponentially damped oscillations can occur only up to a packing fraction η(∗)∼0.718, a val...

We elucidate the connection between various fluctuation theorems by a microcanonical version of the Crooks relation. We derive the microscopically exact expression for the work distribution in an idealized Joule experiment, namely, for a convex object moving at constant speed through an ideal gas. Analytic results are compared with molecular dynamics simulations of a hard disk gas.

Nanoscience has been one of the outstanding driving forces in technology recently, arguably more so in magnetism than in any other branch of science and technology. Due to nanoscale bit size, a single computer hard disk is now able to store the text of 3,000,000 average-size books, and today's high-performance permanent magnets--found in hybrid cars, wind turbines, and disk drives--are nanostru...

We investigate the accretion disc structure in the strongly Comptonised spectra seen at high luminosities from galactic black holes (variously termed the very high or steep power law dominant state). We use simultaneous ASCA-RXTE data on two such spectra from the black hole transient XTE J1550-564 to constrain the disc and Comptonized luminosity. The broad bandpass of the data gives robust esti...

To increase the recording density of hard disk drives (HDDs), it is indispensable to improve the servo track writing (STW) technology that writes the servo positioning information used to position the magnetic recording head onto the data track. Previously, it was popular to write the servo tracks by using the HDD’s own head and positioning it using an external actuator. Recently, however, the ...

We present results from simultaneous optical (SALT) and X-ray (Swift and INTEGRAL) observations of GS 1354-64/BW Cir during the 2015 hard state outburst. During the rising phase, optical/X-ray time series show a strong anti-correlation with X-ray photons lagging optical. Optical and X-ray power spectra show quasi-periodic oscillations at a frequency of ∼ 18 mHz with a confidence level of at lea...

The most common form of storage media utilized in both commercial and domestic systems is the hard disk drive, consequently these devices feature heavily in digital investigations. Hard disk drives are a collection of complex components. These components include hardware and firmware elements that are essential for the effective operation of the drive. There are now a number of devices availabl...

Conventional add-on feedback filters for mid-frequency (mid-f) repeatable runout (RRO) compensation in a hard disk drive (HDD) servo system either have a long filter transient or constitute a large sensitivity hump and poor stability margins. This paper presents a novel linear time-varying (LTV) group filtering scheme for the compensation of a few mid-f RRO harmonics. While having a short filte...

We employ a generalized van der Waals-Onsager perturbation theory to construct a free energy functional capable of describing the thermodynamic properties and orientational order of the isotropic and nematic phases of attractive disc particles. The model mesogen is a hard (purely repulsive) cylindrical disc particle decorated with an anisotropic square-well attractive potential placed at the ce...