Design, Fabrication, and Characterization of Near-Field Apertures for 1 Tbit/in ^ Areal Density

Today, conventional magnetic recording schemes are coming to an end because of the superparamagnetic limit. Heat-assisted magnetic recording (HAMR) may ultimately extend data densities beyond 1 TB/in 2 . HAMR systems utilize the phenomenon during which the magnetic properties of the recording media could be locally modified via heating (optionally, by an optical source in the near field) to temperature in the vicinity of the Curie value of the media material. As a result, heat induced by the optical source can temporarily reduce the magnetic coercivity of high anisotropy material to a level attainable by the magnetic writing head, thus making it feasible to record on relatively small ultra-high anisotropy (and thermally stable) grains, consequently enhancing the areal density dramatically. The key challenge is to develop a near-field transducer capable of delivering over 50 nW into a spot diameter of 30 nm. Traditional fiber schemes are barely capable of 0.1 nW. To resolve the issue, a laser diode could be placed with the emitting edge only a few nanometers away from the recording media. The light can propagate through a nanoaperture on the surface of an aluminum-coated emitting edge. This paper will present an experimental study of recording characteristics of various near-field transducers fabricated via focused ion beam (FIB). To count the number of photons emitted in the near field, a scanning near-field optical microscopy system has been implemented. The experiments indicate that the FIB-fabricated transducers could deliver power of over a few microwatt into a 30-nm spot (Fig. 7)

Protein-based disk recording at areal densities beyond 10 terabits/in.(2)

The concept of optical protein-based memory has been of interest since the early 1970s. Yet, no commercially available protein-based memory devices exist. This review presents an analysis of the main challenges associated with the practical implementation of such devices. In addition, the discussion includes details on the potential of using the unparalleled properties of photochromic proteins by creating an optical data storage disk drive with unmatched features and, particularly, record-high data densities and rates

Perpendicular Recording with Reduced Skew Angle Sensitivity

A detailed analysis to the problem of skew angle sensitivity in perpendicular magnetic recording is presented. A proposed analytical model is supported by numerical simulations with a commercial boundary element software program. According to the presented equivalent magnetic circuit model, a single pole recording head with a laminated composition involving two layers of different magnetic materials could be used to localize adequately strong magnetic field in the vicinity of the trailing edge of the recording head. It is shown that the recording field generated under each lamination layer is proportion to the relative magnetic permeability of the respective layer. Such localization of the magnetic flux results in substantially reduced skew angle sensitivity

Multilevel three-dimensional nanomagnetic recording

The paper outlines a review of multilevel (ML) and three-dimensional (3D) magnetic recording-a nanomagnetic recording technology suitable for information storage densities above 100 terabit/in(2). To comply with the multilevel signal configuration, ML magnetic recording exploits a 3D head/media system powered with next-generation data coding methods. It is believed that combined with novel information processing techniques, relatively cost-effective ML systems could be scaled down to a single-grain spin level thus enabling memory with effective areal densities above 100 Terabit/in(2)

Nanomagnetic probes to image patterned media for information densities beyond ten terabit-per-square-inch

The communication illustrates how focused ion beam-modified nanomagnetic probes could be used to image patterned media with the resolution of a few nanometers only and thus suitable for densities above 10 terabit/in(2) . To take advantage of the modified probes, the measured signal is deconvolved with the sensitivity field inherent to the probe. Focused ion beam is used to trim silicon probes into the probes with the adequate geometry to satisfy the requirements on the sensitivity field. The measurements indicate that the resolution of magnetic force microscopy could be made comparable with the resolution of atomic force microscopy

Physics of perpendicular recording with a patterned soft underlayer

In this paper, it is argued that perpendicular recording in the most popular current form--with the use of a continuous soft underlayer (SUL)--may not be the most optimal way to maximize the achievable areal density. As a possible solution, patterning of SUL is discussed. The purpose of patterning of a SUL is to effectively move the image head closer to the recording media, as compared to the real recording head, and thus increase the net recording field and the field gradient across the thickness of the media. Various patterning configurations and combinations with recording layers are comparatively studied. It is illustrated that with a patterned SUL, the recording and sensitivity fields, responsible for writing and reading information, respectively, could be not only increased by several factors but also localized across the entire thickness of the recording media

Near-field optical transducer for heat-assisted magnetic recording for beyond-10-Tbit/in(2) densities

Continuous device downscaling, growing integration densities of the nanoscale electronics and development of alternative information processing paradigms, such as spintronics and quantum computing, call for drastic increase in the data storage capacity. In this paper we review our recent results for the design, fabrication and characterization of the near-field optical transducer for heat-assisted magnetic recording for beyond the 10-Tbit/in(2) densities. In order to record information, the heat-assisted magnetic recording system uses not only magnetic but also thermal energy. For this reason the recording media with the substantially higher anisotropy could be utilized to achieve the ultra-high recording densities. In this review, we provide details of the design of the near-field transducer capable of delivering over 50 I-LW power into a spot with the diameter of 30 nm. Heat-assisted magnetic recording and spin-based information processing require accurate thermal management of magnetic thin films. Here we report the results of our preliminary investigation of thermal transport in Pd/CoPd/Pd magnetic multilayers with the thickness of individual layers in the nanometer range

Three-Dimensional Non-Volatile Magnetic Universal Logic Gates

We present an experimental study on ultra-dense 3-D non-volatile magnetic universal logic gates with reconfigurable AND and OR functions. A four-layer magnetic structure with a net thickness of less than 30 nm is employed as a study illustration of a highly scalable magnetic logic device. In the device, the magnetic state of the top output "soft" layer depends on the magnetic states of the remaining three "hard" layers used as two input and one reset layers, respectively. To build vertically oriented magnetic devices with a gradient of the coercivity and the magnetization across the thickness, we use Co/Pd multilayers sputter-deposited via a combinatorial synthesis. Through a focused magneto-optical Kerr effect (F-MOKE) study, we relate input and output states in the 4-layer logic device to shoulders on major and minor M-H hysteresis loops. We use magnetic force microscopy (MFM) to identify magnetic logic operations