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Magneto-optical Kerr effect (MOKE) microscopy and vibrating sample magnetometer (VSM) were used to investigate the magnetic properties of CoFeTaZr and CoTaZr soft magnetic underlayers (SULs). When comparing the CoTaZr with the CoFeTaZr amorphous thin films, the CoFeTaZr films yielded superior magnetic properties. Pre-sputtering substrate Ar-ion milling and sputtering processing pressure were varied to control the magnetic properties of the amorphous films. Furthermore, it was discovered that the magnetic properties of the amorphous thin film strongly depended on the thickness of the SULs, seed layers and capping layers. The experimental results indicated that above a certain thickness, the media noise could be substantially reduced and the magnetic properties of the CoFeTaZr SULs would be optimized. It was also shown that CoFeTaZr SULs with a Ta capping layer and Ru seedlayer had lower coercivity.

We are working on developing special nanoprobes and techniques to improve the resolution of Magnetic Force Microscopy, MFM. In this paper we describe the custom probes fabricated at our lab and a mathematical algorithm to improve the resolution of the images obtained with these probes. The algorithm is based on physical principles and not on statistical nor on digital signal processing techniques. Our method consists in reversing the non-uniform interaction that takes place between the magnetized probe tip and the perpendicular magnetic stray field produced by the magnetized sample. We developed a compensation field that when scanned over the originally data points produces the effect of imaging the magnetic field with a flat response probe tip. Using this method we obtained images of higher resolution than those provided by conventional MFM.

We use ion beam proximity lithography (IBPL) to produce 4 mm times 4 mm arrays of 220-nm dots in perpendicularly oriented Co/Pd multilayered media. A novel technique of overlapping neighbors is used with IBPL to generate samples with controllable size distribution sigmaD of the nanoarrays. The switching field distribution sigmaHcr/HCr is measured for each sample before and after irradiation, and a linear relationship is experimentally found between sigmaHcr/HCr and sigmaD. Empirical calculations support our determination that self-demagnetization fields are responsible for a portion of the switching field distribution. Using the zero intercept of the experimental data, we find the inherent anisotropy distribution in the Co/Pd samples is on the order of 10%. We further irradiate the samples with He+ ions to alter the anisotropy and better understand the role of shape anisotropy. As interface anisotropy is reduced in the Co/Pd bit-patterned medium (BPM) samples, shape anisotropy has a much greater contribution on the switching field distribution of the BPM samples.

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.

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/in2. 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).

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.

FePd thin films were electrodeposited from ammonium citrate complex baths. The effects of various electrodeposition and post heat treatment conditions including pH, current density, bath concentrations, substrates and annealing temperature on composition, material, and magnetic properties were systematically investigated. In these baths, the deposited iron content increased linearly with an increase in current density from 1 to 5 mA cm −2 producing films with compositions extending from Fe 7 Pd 93 to Fe 91 Pd 9 . Magnetic saturation ( M S ) of electrodeposited FePd thin films linearly increased with increase in deposited iron content (i.e. ∼1.8 T for Fe 82 Pd 18 and ∼0.1 T for Fe 19 Pd 81 ) which is similar to its bulk counterparts. The effects of post-heat treatment on the phase and crystal structure of near equiatomic FePd electrodeposits (i.e. Fe 48 Pd 52 ) was investigated by subjecting electrodeposits to different annealing temperatures from 400 to 600 °C under reducing environment. L1 0 FePd phase was formed from nanocrystalline FePd solid solution and the crystallinity improved with increasing annealing temperatures.

The need to incorporate advanced engineering tools in biology, biochemistry and medicine is in great demand. With the rapid emergence of nanotechnologies during the past decade, it is becoming hard to deny the great impact the new technologies can make on our everyday life and especially the fields of biology and medicine. In this review article, we discuss one such technology, nanoliter-volume nuclear magnetic resonance spectroscopy (NMR), which could be used for chemical signature-based detection of ultra-small quantities of biomolecules. NMR spectroscopy has been used by biochemists for over two decades. However, conventional NMR spectrometers are relatively costly, bulky and often require special laboratory environment for their proper operation. Such NMR systems require ultra-high magnetic field, i.e., of the order of several Tesla, in a relatively large volume and therefore require special shielding and installation. The major challenge for successful scaling of the conventional NMR systems down to the nanoscale range is the difficulty in maintaining adequate (for reasonable signal detection) signal-to-noise ratio (SNR). This paper discusses a new technology aimed to develop NMR spectrometers that not only could be scaled down to the nanoscale range but also could operate with adequate SNR at field strengths as low as 1/4 Tesla. The largest physical component of this system is a ring-shaped permanent magnet that has an outer diameter of 40 mm. The system was designed via computer simulations to consider the magnetostatic interactions between relatively components of the system (magnets, coils, sensors, shields, and so on) and also spin dependent nanoscale magnetic devices which could be used to further boost the net signal to noise ratio of the system. Particularly, a special tunneling magneto-resistive sensor array was designed to achieve the goal of further increasing SNR. The computational tools include direct digital synthesis to generate RF signals with an ultra-high frequency precision, digital signal processing to filter and condition the retrieved NMR signal and a special backpropagation neural network based computer chip to find the optimum match for the NMR spectrum of a sample under investigation. This portable NMR system is intended to analyze samples with volumes as small as a few hundreds of nanoliters at room temperature. In the future, the discussed technology could be further developed to detect a wide range of chemicals at a single-molecule level.

Recording physics, design considerations, and fabrication of bit-patterned magnetic medium for next generation data storage systems is presented. (Co/Pd)N magnetic multilayers are evaluated as candidates for bit-patterned medium recording layer materials for their high and easily tunable magnetic anisotropy. The optimized patterned multilayers used in this study had coercivities in excess of 12-14 kOe. Bit patterning was accomplished using ion-beam proximity printing, a high-throughput direct write lithography where a large array of ion beamlets shaped by a stencil mask is used to write an arbitrary device pattern. It is found that the nature of magnetization reversal strongly depends on bit edge imperfections and is likely to contribute to switching field distribution.

Recording physics, design considerations, fabrication, and characterization of bit-patterned magnetic medium for next generation data storage systems is presented. (Co/Pd) N magnetic multilayers are evaluated as candidates for bit-patterned medium recording layer materials for their high and easily tunable magnetic anisotropy. Optimized patterned multilayers used in this study had coercivities in excess of 12-14 kOe. Bit patterning was accomplished using ion-beam proximity printing, a high-throughput direct write lithography where a large array of ion beamlets shaped by a stencil mask is used to write an arbitrary device pattern. It is found that the nature of magnetization reversal strongly depends on bit edge imperfections and is likely to contribute to switching field distribution.

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 μW 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.

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.

Magnetic logic devices have advantages of non-volatility, radiation hardness, scalability down to the sub-5-nm range, and three-dimensional (3D) integration capability. Despite these advantages, nanomagnetic applications for information processing are limited today. The main stumbling block is the inadequately high energy required to switch information states in the spin-based nanodevices. Recently, the spin-transfer torque (STT) effect has been introduced as a promising solution [1-2]. In STT magnetic tunneling junctions (MTJs), using a spin-polarized electric current to switch magnetic states has the potential to solve the energy problem. However, the switching current density on the order of 1 MA/cm2 in the current STT-MTJ devices, with the smallest reported to date characteristic cross-sectional size on the order of 10 nm, still remains inadequately high for enabling a wide range of information processing applications [3-4]. For the technology to be competitive in the near future, it is critical to show that it could be favorably scaled into the sub-10-nm range. On a positive note, due to a new physics in this previously poorly explored size range, nanomagnetic devices may display promising characteristics that can make them superior to their semiconductor counterparts. In this size range, the underlying spin physics is due to the surface as much as it is due the volume. As a result, the effective thermal reservoir that absorbs spin excitations is substantially reduced, which in turn leads to a reduced spin damping and consequently to a reduced switching current density. Hence, the current study to understand the junction size dependence of the spin switching current is timely. This paper presents the key results of this study.

An approach to fabrication of a patterned magnetic recording medium for next generation data storage systems is presented. (Co/Pd)n magnetic multilayers are evaluated as candidates for patterned medium materials for their high and easily controllable magnetic anisotropy. The multilayer films deposited on a Ta seed layer enable high intergranular exchange coupling—an essential feature of a patterned magnetic recording medium. The quality of (Co/Pd)n superlattices was optimized via deposition conditions and monitored using low-angle x-ray diffraction. An estimated in-plane (hard-axis) magnetization saturation field in excess of 40 000 Oe was observed. Vertical (easy-axis) hysteresis loops for as-deposited continuous magnetic multilayers exhibited a low coercivity of 930 Oe, indicating highly uniform (magnetically) films with weak domain wall pinning. Ion-beam proximity lithography was used to pattern magnetic multilayers into 43 nm islands on a 135 nm pitch. Following patterning, easy-axis coercivity increased nearly 15-fold to 12.7 kOe.

This work presents a study of Ga+ ion implantation of polycrystalline hcp cobalt thin films and nanostructures. It is shown that Ga+ ion implantation leads to a substantial modification of magnetic properties including large coercivity increase and shearing of in-plane magnetization loops suggesting the introduction of domain wall pinning sites and the reduction of intergranular exchange coupling. Because ion implantation can be accompanied by substantial heat dissipation, it is discussed how the annealing effects can be minimized. Application of ion implantation to selectively tailor properties of magnetic nanostructures is demonstrated.

Magnetic force microscopy (MFM) is a widely used form of scanning probe microscopy (SPM) that is used for obtaining a magnetic image from a surface with nanoscale resolution. Currently, the resolution of MFM is limited to approximately 20 nm due to the long-range nature of magnetic interactions between the MFM probe's tip and the magnetic medium. This paper describes an optimal signal processing solution to the problem of achieving high resolution MFM with the goal of significantly exceeding the level at which MFM metrology currently performs, thus providing metrologists with a means of resolution increase that is believed will enable, for example, the rapid development of high-density magnetic recording media (>100 Gbit in−2). This is achieved by using focused-ion beam trimming of a conventional tip to create a probe tip of predictable magnetic characteristics and then, provided that the sample could be approximated as a thin-film, using knowledge of this tip's sensitivity field for performing a deconvolution on the measured signal to better estimate the magnetic state of the surface under study. Stated differently, as the MFM measured signal is modelled as the convolution of the magnetized surface and the tip's sensitivity field, we exploit knowledge of the tip's properties to increase the resolution of the MFM image. Details of the deconvolution approach as well as images resulting from this processing are the focus of this paper.

In this article, a detailed overview of the methodology to design a write transducer for recording onto perpendicular media at areal densities beyond 1 Tbit/in.2 is presented. The two basic modes of perpendicular recording, single-layer recording media in combination with a ring type head and double-layer recording media with a soft underlayer in combination with a single pole head, are compared with each other theoretically and experimentally. Moreover, perpendicular recording is compared to longitudinal recording from the perspective of the writing process. The system efficiency is redefined for perpendicular recording to take into account the critical role of the soft underlayer. The effects of using “soft” magnetic shields around the trailing pole are analyzed. It is shown that at least a factor of 2 increase in the field can be obtained at areal densities beyond 500 Gbit/in.2 if shields are used. Such an open issue as the skew angle sensitivity in perpendicular recording is analyzed. It is shown that...

In this tutorial, focused-ion-beam (FIB)-based fabrication is considered from a very unconventional angle. FIB is considered not as a fabrication tool that can be used for mass production of electronic devices, similar to optical and E-beam—based lithography, but rather as a powerful tool to rapidly fabricate individual nanoscale magnetic devices for prototyping future electronic applications. Among the effects of FIB-based fabrication of magnetic devices, the influence of Ga+-ion implantation on magnetic properties is presented. With help of magnetic force microscopy (MFM), it is shown that there is a critical doze of ions that a magnetic material can be exposed to without experiencing a change in the magnetic properties. Exploiting FIB from such an unconventional perspective is especially favourable today when the future of so many novel technologies depends on the ability to rapidly fabricate prototype nanoscale magnetic devices. As one of the most illustrative examples, the multi-billion-dollar data storage industry is analysed as the technology field that strongly benefited from implementing FIB in the above-described role. The essential role of FIB in the most recent trend of the industry towards perpendicular magnetic recording is presented. Moreover, other emerging and fast-growing technologies are considered as examples of nanoscale technologies whose future could strongly depend on the implementation of FIB in the role of a nanoscale fabrication tool for rapid prototyping. Among the other described technologies are 'ballistic' magnetoresistance, patterned magnetic media, magnetoresistive RAM (MRAM), and magnetic force microscopy.

This work investigates various types of reader designs as applied to magnetic recording. Reciprocity principle is used to study playback response. It is shown that both shielded and not shielded differential readers exhibit magnetic playback properties advantageous for achieving extremely high areal bit densities. Modified design of differential readers with one MR sensor is proposed to overcome the manufacturability issues associated with a conventional double-MR sensor differential reader.

The physics of the playback process in perpendicular recording is explored. It is shown that due to the existence of effectively two layers of the “magnetic charges” in a perpendicular medium, the stray field sensed by a reader rolls off with the areal density essentially differently than it does in longitudinal recording. Comparing three recording modes, longitudinal recording and perpendicular recording without and with a soft underlayer (SUL), at equivalent conditions, with a 10 nm thick recording layer at a bit aspect ratio of 1:1, the density roll-off is the fastest for the longitudinal mode, while it is the slowest for the perpendicular mode without a SUL. It is shown that although at relatively low linear and track densities the use of a SUL increases the playback signal, the signal does not depend on the use of a SUL at high densities. It is shown that for both perpendicular modes, although at sufficiently low track densities (below ∼50 ktpi) the signal disappears at relatively low linear densitie...

Summary form only given. At high data rates a transition from thermo-activated to gyro-magnetic magnetic switching occurs. The switching is then driven mainly by the head field and thermal effects are usually ignored. In this study, it is shown that when the field from a recording head does not change polarity and no transition is written, the switching of the magnetization for current recording media occurs by thermal activation. The magnetic response of individual grains during the motion through the field profile of the recording head is determined by integration of the Langevin equation of the system using the Heun numerical scheme. The authors show that the thermal reduction of the switching field exhibits a logarithmic variation with medium velocity v, characteristic of a thermo-activated process, when v v/sub 1/, the thermal reduction of the switching field is independent of the medium velocity but linearly dependent on temperature and is attributed to random variations in the realization of the gyro-magnetic switching process. For v

Magnetic force microscopy measurements of perpendicular media with a CoCr-based hard layer and a CoFe soft underlayer has been made to investigate skew angle effects. The recorded tracks were produced using a focused ion beam made single pole head with a track width of approximately 400 nm and a gap thickness of approximately 1 μm at a 25 nm flying height. Magnetic force microscopy images of tracks recorded at write currents above and below the saturation value of approximately 100 mA turn were studied at different values of the linear density, 20–100 kfci, at zero skew angle as well as −15° and +15°. Calculated perpendicular recording fields versus the distance down the track, and across the track, near the trailing pole edge was performed using three-dimensional boundary element modeling and compared to the results from the microscopy data. Drawbacks and possible solutions to the skew angle problem for perpendicular recording are discussed.

Conformal mapping was applied to derive the concept of the playback waveform equivalency between a shielded read head and a dual pole head utilized for reading from longitudinal and perpendicular media, respectively. The equivalency relationships between the respective head dimensions were defined. To support the concept in 3D, 3D-boundary element calculations were performed to calculate the sensitivity fields corresponding to both the head types.

The long-term stability of a CoCrPt perpendicular storage media has been investigated by thermal aging at temperatures ranging from 95 to 280 °C during otherwise normal ambient conditions. The signal-to-noise ratio from magnetic force microscopy images has been extracted by the autocorrelation method and compared for the different aging conditions. During aging at elevated temperatures, the media stack undergoes some structural and crystallographic changes. It is found that the severity of the aging process is higher for low-density bit patterns due to the higher value of demagnetizing fields for large bits. A comparison to the thermal aging is done with a set of disks in which a deterioration of the magnetic bit pattern was induced by an external magnetic field. Two experiments, including fields with a single polarity as well as with a cycled polarity, mimic different magnetic situations for the disk. During the external field experiments, no structural or crystallographic changes occur in the media. The magnetic background noise of the disks is also analyzed. For aging in a magnetic field, it is found that below a certain threshold value, mostly low-density bit patterns are affected by the aging process. However, above the threshold value, both low and high-density bit patterns are affected.

A focused ion beam (FIB) process can be utilized not only for etching but also for deposition at dimensions in the nanoscale range. In this paper, a ring-type magnetic head with dimensions in the nanoscale range was fabricated via FIB etching followed by FIB deposition of non-magnetic tungsten into the etched trenches. As a result, magnetic pole tips each with a cross-section as narrow as 140 × 60 nm2 and with a length as tall as 500 nm were protected and supported from all the sides. Direct observation of the 'easy' magnetization switching via magnetic force microscopy verified that favourable magnetic properties were preserved during such nanoscale processing.

Summary form only given. It is commonly believed that to achieve high recording performance, the gap between the leading and trailing poles in a single pole head (SPH) has to be long with respect to the . Such an SPH is referred to as type I. An SPH in which the gap length is small air bearing surface (ABS) to soft underlayer (SUL) spacing with respect to SUL-to-ABS spacing is referred to as type II. In this work, the recording characteristics of type II and type I SPHs are compared. For clarity, SPH and RH imply the presence and the absence of a SUL, respectively. It should be stressed that recording on a medium with a RH is fundamentally different from recording with a SPH. In recording with a SPH, the writing is done by the trailing edge of the trailing pole. This is in contrast to recording with a RH, in which the writing is done by the trailing edge of the gap. A conventional RH used to write onto a medium with a SUL acts as a type II SPH.

In this paper, we describe techniques for the magnetic characterization of perpendicular recording media. Such measurements made using traditional techniques, such as the vibrating sample magnetometry (VSM) and alternating gradient force magnetometer (AGFM), have to be corrected for the sample shape demagnetizing factor, which is often found not to be equal to -4/spl pi/. For measurements other than the simple hysteresis loop, such as remanence curves, this correction must be carried out in real time and we describe the method by which this can be achieved and the process for achieving the correct demagnetization of perpendicular films prior to measurements of the isothermal remanent magnetization curve. A further complication is that real perpendicular media have a soft underlayer beneath the recording layer, which swamps and confuses signals from instruments such as VSM or AGFM. Hence, we describe the construction and use of a magnetooptical Kerr effect magnetometer, which does not penetrate significantly into the soft layer and enables the perpendicular layer to be measured independently. We describe the properties of a traditional alloy perpendicular medium and a Co-Pd multilayer system, which in the latter case exhibits multiple switching behavior. We also address the issue of the effect of the soft underlayer on the coupling in similar longitudinal films and find that the presence of the underlayer induces significant additional coupling effects that may well give rise to an increase in noise in recorded signals.

Signal-to-noise ratio (SNR) from a limited bit sequence has been extracted from magnetic force microscopy (MFM) images by two different methods and compared. The autocorrelation SNR properties extracted from the MFM image data are in better agreement with spinstand data than “normal” Fourier extracted SNR values. Transition noise data were also extracted and analyzed, “Squeezing” of the noise was measured as the periodicity of the recorded bit pattern became smaller than 250 nm and subsequently a relaxation at ∼200 nm occurred. MFM analysis based SNR data for two media types (CoCrPtTa alloy and CoB/Pd multilayer based) are compared. Ni45Fe55 alloy was used for the soft underlayer material.

Using 3D-boundary element modeling, guidelines for designing an ultra-high density perpendicular system were defined. Both geometrical and material influences were investigated. The theoretical principles developed to choose dimensions and materials were experimentally verified using a wafer test structure and spin-stand experiments with a 60 nm wide focused ion beam trimmed head.

Focused ion beam (FIB) applications in the field of nanoscale probe recording are explored. A detailed description of how to use FIBs for trimming longitudinal and perpendicular magnetic recording and playback devices to dimensions of less than 100 nm is presented. An experiment was conducted to demonstrate that the magnetoresistive property of a read element, e.g. a giant-magnetoresistive sensor, strongly depends on the focused ion current and the beam accelerating voltage.

The results of both theoretical and experimental studies of some of the key issues related to the hard layer in perpendicular magnetic recording are presented. Among the discussed issues are the guidelines and underlying physics for choosing the optimized recording layer parameters such as thickness, specific magnetic properties, types of recording layer material, etc. Special attention is given to the physical phenomena and parameters that define the optimum thickness of the recording layer. To stress the specific aspects of the recording physics native only to perpendicular recording, a comparison between perpendicular and longitudinal media is carried out throughout the work.

Introduction: Delivering a drug specifically into the tumor cell past its membrane and then releasing the drug into the tumor cells without affecting the normal cells remains a formidable challenge. Unlike any other nanoparticles, magnetoelectric nanoparticles (MENs) display a non-zero magnetoelectric (ME) effect and thus present a unique capability to use external magnetic fields to control intrinsic electric fields associated with cell membranes and the interaction between MENs and therapeutic loads. Because cancer and normal cells of the same type have different electric properties, MENs is used for high-specificity targeted delivery. An a.c. magnetic field is used to trigger drug release off the nanoparticles. Brief Methods: 30-nm CoFe2O4-BaTiO3 core shell MENs, with a magnetization of 1 emu/g, a coercivity of 300 Oe, and a ME coefficient of 10-100 mV cm-1 Oe-1 were prepared with a coprecipitation process. MENs were coated with fluorescein isothiocyanate to monitor their intra-cellular transport through a high-contrast confocal microscopy. Three cancer cell lines including Skov-3 (Ovarian adenocarcinoma), U87-MG (Glioblastoma), and MCF-7A (Breast adenocarcinoma), and two normal cell lines including brain endothelial cells (Brain EC) and ovarian cells HOMEC were cultured at 37°C. The transport of MENs loaded with drugs, peptides, and RNAs through the cell membranes and the consequent release of the load under different d.c. and a.c. magnetic fields were studied through confocal microscopy and photoabsorption spectroscopy, respectively. Trypan-blue viability count was used to assess cell growth inhibition under different study conditions. Atomic force microscopy of the cell membranes was conducted to understand the interaction between the nanoparticles and the cells. Summary of new data: Comparison of MENs with purely magnetic iron oxide nanoparticles showed that the penetration through the cancer cell membrane could be achieved only with MENs. It took d.c. fields of 100 Oe and over 1000 Oe to nanoelectroporate the membranes of SKOV-3 and HOMEC cell lines, respectively. An a.c. magnetic field with a strength of 50 Oe and a near-d.c. frequency of 100 Hz was sufficient to enable release of a therapeutic load off MENs. All the cancer cell lines under study showed membrane penetration threshold d.c. fields at least a factor of ten smaller compared to their normal counterparts. Conclusion: MENs displayed unique capabilities for externally controlled high-specificity targeted anticancer drug delivery and release on demand via application of d.c. and a.c. magnetic fields, respectively. Because MENs rely on a physical mechanism rather than antibody-mediated delivery, they can be used for high specificity delivery and high-efficacy controlled release of a broad range of therapeutic loads including drugs, peptides, and RNAs to treat many different cancers. Citation Format: Emmanuel Stimphil, Abhi Nagesetti, Tiffanie S. Stewart, Alexa Rodzinski, Rakesh Guduru, Ping Liang, Carolyn Runowicz, Sakhrat Khizroev. Magnetoelectric nanoparticles for high-specificity treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2199. doi:10.1158/1538-7445.AM2017-2199

In regard to cancer therapy, magnetoelectric nanoparticles (MENs) have proven to be in a class of its own when compared to any other nanoparticle type. Like conventional magnetic nanoparticles, they can be used for externally controlled drug delivery via application of a magnetic field gradient and image-guided delivery. However, unlike conventional nanoparticles, due to the presence of a non-zero magnetoelectric effect, MENs provide a unique mix of important properties to address key challenges in modern cancer therapy: (i) a targeting mechanism driven by a physical force rather than antibody matching, (ii) a high-specificity delivery to enhance the cellular uptake of therapeutic drugs across the cancer cell membranes only, while sparing normal cells, (iii) an externally controlled mechanism to release drugs on demand, and (iv) a capability for image guided precision medicine. These properties separate MEN-based targeted delivery from traditional biotechnology approaches and lay a foundation for the comp...

A scanning magnetoresistance microscope (SMRM) was used to enable recording experiments on bit patterned media prototypes not yet suitable for spin-stand evaluation. The SMRM generates a 2D playback response of the media by “dragging” a recording head across the sample using a piezoelectric nanopositioner. A large-scale parameter optimization technique is applied to extract relevant parameters such as pulse amplitude, pulse width, and pulse position from the 2D playback response. The parameters were analyzed to learn that the pulse response of our recording head cannot be accurately modeled as a Gaussian function. The error in the optimized parameters is dominated by intertrack interference and to a lesser extent measurement resolution and thermal drift.

Using 3D modeling, guidelines for ultra-high density perpendicular recording were defined. The concepts developed to choose dimensions and materials were verified experimentally using MFM and spin-stand experiments with a 60 nm wide focused ion beam (FIB) trimmed head.

The effect of the relative head-to-medium velocity on the switching dynamics of individual grains is studied using the Landau-Lifshitz-Gilbert equation of motion. The coercive field of a grain may increase or decrease with velocity depending on the direction of crystal anisotropy. An asymmetry is present and the coercivity of an ensemble of grains with random in-plane anisotropy is found to increase, in agreement with measurements on a CoCr longitudinal magnetic recording medium.

CoCrPtTa/Ti bilayer thin films have been sputter deposited onto both glass and Al substrates under high sputtering rate in a manufacturing environment. From microstructure and magnetic property studies, it is found that Cr segregation and stacking fault density are the two major issues in obtaining high quality perpendicular media. (0002) texture orientation spread and c lattice parameter remain almost constant within the variation range of the deposition parameters, though there is a small distinction between the media on glass and those on Al substrates.

The results of both theoretical and experimental studies of some of the key aspects of the recording physics specific to perpendicular media with a soft underlayer are presented. Some of the discussed issues are the material requirements for the preferred soft underlayer design such as the role of magnetic anisotropy, the proper choice of the magnetic moment, and the control of the soft underlayer noise.

The absorption properties of optical protein memories, comprised of Bacteriorhodopsin (BR) monolayer films, were studied for the first time to better understand the underlying read/write processes. We demonstrate that 755 nm light provides the greatest difference between the bR and Q photostates in 2D BR films. This implicates 755 nm as an optimal wavelength for probing the state of monolayer BR. A Cary 5000 spectrometer was used to observe state changes via absorption measurements following LED irradiation of BR coated samples.

This paper reviews the material properties of Fe-AlN high moment soft magnetic material, and discusses the design, fabrication and performance of write heads using this material. These write heads comprise two designs. The first had FeAlN for both top and bottom poles. The second incorporated a 0.2 /spl mu/m thick FeAlN layer underneath an electroplated Ni/sub 80/Fe/sub 20/ top pole. The first type of head was tested on high coercivity (3300 Oe) media. Wide and narrow track width heads saturated the media at the highest tested write frequency of 225 MHz. At 90 MHz, they exhibited overwrite approaching 50 dB and hard transition peak shift of less than 1 nm. This overwrite was 7-9 dB higher than that measured for heads with Ni/sub 45/Fe/sub 55/ top poles. A 50% amplitude roll-off density (D/sub 50/) of up to 6300 fc/mm was also measured, using a narrow gap MR read sensor. However, reverse dc erase noise measurements indicated significantly lower head efficiency compared to NiFe heads, as has been observed previously. The second type of head on the other hand exhibited /spl sim/5 dB better overwrite compared to a Ni/sub 80/Fe/sub 20/ head, without a large loss in head efficiency.

Focused ion beam (FIB) milling is a well-established technique for micro- and nano-fabrication of prototype media and devices. However, the key advantages of this method must be carefully balanced against its inherent problems such as ion implantation to the treated matrix and secondary deposition of the milled material. In this work, we report the effect of Ga + ion implantation in multilayer CoPd matrix on the materials' magnetic properties. The dependence of the effect on both the irradiation dosage and the ion energy is studied. We observe a significant effect at irradiation doses as low as 1* 10 14 ions/cm 2 , approximately 10 times lower than previously reported. However, the total magnetic moment of the medium is not affected, while the anisotropy of the material changes from out-of-plane to in-plane. No effect of implantation is observed at ion energies at and below 5 keV.

Micromagnetic modeling based on LLG formalism was used to study the magnetization reversal processes in patterned recording layer. The write fields generated by an idealized single pole write head with a uniformly magnetized air-bearing surface (ABS) were used. The applied write field is highly nonuniform within a bit, making consistent comparison based on its values difficult. The effects of the bit geometry, medium thickness, head/medium magnetic spacing (flying height), ABS geometry, the effects of neighboring bits on magnetization reversal, and the sensitivity of the write process to non-zero write misregistration (WMR) were investigated. It was shown that the larger ABS cross-section heads generate stronger write fields resulting in a capability of using higher anisotropy/better thermal stability media materials. Also, the sensitivity on WMR is weaker for larger ABS cross-section heads simplifying the optimization of a recording system design.

Perpendicular recording may be the most viable, near future, replacement for the longitudinal core technology in ultrahigh-density magnetic disk storage. Central to this mode of recording is a soft underlayer (SUL) which facilitates flux flow between writer poles, and is responsible for an effective increase in recording field. However, there are controversies concerning the effectiveness and limitations of using soft underlayers; among which are readback noise and inadequate switching torque. Patterned SUL is proposed as a new and viable approach to SUL limitations in perpendicular media, with improved system performance. Numerical models have been developed using commercially available FEM and BEM software suites (ANSYS and Ampere) to demonstrate key advantages of patterned SUL in perpendicular media

Magnetoresistive playback off bit patterned magnetic recording media is studied. Three playback configurations are compared: not shielded sensors, shielded sensors commonly used in magnetic recording systems, and shielded differential sensors. Influence of patterned medium parameters including bit-filling ratio, bit shape, bit position jitter, bit-size variation on the playback signal is studied. Playback signal amplitude, D50, and signal-to-noise ratio are used to compare different playback sensor configurations. It is found that in general, shielded differential readers offer superior performance as compared to both shielded single sensor readers and not shielded readers

Carbon-based magnetic materials and structures of mesoscopic dimensions may offer unique opportunities for future nanomagnetoelectronic/spintronic devices. To achieve their potential, carbon nanosystems must have controllable magnetic properties. We demonstrate that nitrophenyl functionalized graphene can act as a room-temperature 2D magnet. We report a comprehensive study of low-temperature magnetotransport, vibrating sample magnetometry (VSM), and superconducting quantum interference (SQUID) measurements before and after radical functionalization. Following nitrophenyl (NP) functionalization, epitaxially grown graphene systems can become organic molecular magnets with ferromagnetic and antiferromagnetic ordering that persists at temperatures above 400 K. The field-dependent, surface magnetoelectric properties were studied using scanning probe microscopy (SPM) techniques. The results indicate that the NP-functionalization orientation and degree of coverage directly affect the magnetic properties of the graphene surface. In addition, graphene-based organic magnetic nanostructures were found to demonstrate a pronounced magneto-optical Kerr effect (MOKE). The results were consistent across different characterization techniques and indicate room-temperature magnetic ordering along preferred graphene orientations in the NP-functionalized samples. Chemically isolated graphene nanoribbons (CINs) were observed along the preferred functionality directions. These results pave the way for future magnetoelectronic/spintronic applications based on promising concepts such as current-induced magnetization switching, magnetoelectricity, half-metallicity, and quantum tunneling of magnetization.

Nature Communications 4: Article number: 1707 (2013); Published: 16 April 2013; Updated: 25 October 2013. This Article contains typographical errors in the second paragraph of the Results section and the first paragraph of the Discussion section. In each case the magneto-electric (ME) coefficient ofthe nanoparticles was incorrectly cited in V cm −1 Oe −1, whereas the value should have been 100 mV cm −1 Oe −1.

The nanotechnology capable of high-specificity targeted delivery of anti-neoplastic drugs would be a significant breakthrough in Cancer in general and Ovarian Cancer in particular. We addressed this challenge through a new physical concept that exploited (i) the difference in the membrane electric properties between the tumor and healthy cells and (ii) the capability of magneto-electric nanoparticles (MENs) to serve as nanosized converters of remote magnetic field energy into the MENs' intrinsic electric field energy. This capability allows to remotely control the membrane electric fields and consequently trigger high-specificity drug uptake through creation of localized nano-electroporation sites. In in-vitro studies on human ovarian carcinoma cell (SKOV-3) and healthy cell (HOMEC) lines, we applied a 30-Oe d.c. field to trigger high-specificity uptake of paclitaxel loaded on 30-nm CoFe2O4@BaTiO3 MENs. The drug penetrated through the membrane and completely eradicated the tumor within 24 hours without affecting the normal cells.