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Spin-transfer torque (STT) magnetization reversal in a magnetic tunneling junction (MTJ), Ta/CoFeB/MgO/CoFeB/Ta, built on the tip of a nanoprobe in a direct contact with a copper substrate is demonstrated in the previously unexplored sub-10-nm diameter range. With the contact resistance of the order of 185 kOhm, the measured magnetoresistance value was 29 %. The average STT reversal current of 95 nA indicated a switching current density of approximately 0.1 MAcm−2 which is more than 30 times smaller than the smallest value reported for STT-MTJs of larger dimensions. An atomistic-scale theory confirmed the experimental result which indicates at least an order of magnitude reduction of the spin damping in the sub-10-nm diameter range.

Focused ion beam (FIB) is used to implant Ga+ ions into a 30-nm thick magnetoresistive element to effectively reduce the track width of the sensor from 1 µm to ~80 nm. Through magnetic recording industry-standard spinstand measurements, it is confirmed that a dose of ~103 ions/cm2 at a 1-pA FIB current is sufficient to fully “de-activate” magnetism in the exposed side regions. To record tracks required for spinstand tests, a FIB-trimmed ring type write head is used.

Using a Heisenberg model along with Monte Carlo, it is demonstrated that localized domain walls can be formed inside nanoconstrictions. The origin of the localized domain wall lies in the competition between atomic-scale exchange and the shape anisotropy. This leads to high sensitivity of the domain wall width on the shape of the nanoconstriction. Moreover, it is shown that ferromagnetic ordering is considerably reduced in these localized domain walls.

Although highly active anti-retroviral therapy has resulted in remarkable decline in the morbidity and mortality in AIDS patients, inadequately low delivery of anti-retroviral drugs across the blood-brain barrier results in virus persistence. The capability of high-efficacy-targeted drug delivery and on-demand release remains a formidable task. Here we report an in vitro study to demonstrate the on-demand release of azidothymidine 5'-triphosphate, an anti-human immunodeficiency virus drug, from 30 nm CoFe2O4@BaTiO3 magneto-electric nanoparticles by applying a low alternating current magnetic field. Magneto-electric nanoparticles as field-controlled drug carriers offer a unique capability of field-triggered release after crossing the blood-brain barrier. Owing to the intrinsic magnetoelectricity, these nanoparticles can couple external magnetic fields with the electric forces in drug-carrier bonds to enable remotely controlled delivery without exploiting heat. Functional and structural integrity of the drug after the release was confirmed in in vitro experiments with human immunodeficiency virus-infected cells and through atomic force microscopy, spectrophotometry, Fourier transform infrared and mass spectrometry studies.

Background: Despite significant progress in targeted drug delivery, glioblastoma is one of the least treatable tumors today. Delivering therapy across the blood-brain barrier (BBB) and overcoming resistance of tumor cells to current treatments remains a formidable task. The objective of the current in vitro and in vivo study was to show how a new class of multifunctional nanoparticles termed magnetoelectric nanoparticles (MENs) are used to achieve high-efficacy delivery of a therapeutic load across BBB, then release the load on demand, without affecting normal cells, via application of a specially tailored command sequence of D.C. and A.C. magnetic fields. Methods: Growth hormone (GH)-releasing hormone (GHRH) antagonists, a class of anti-tumor peptides, block the release of tumorigenic insulin-like growth factors. Glioblastoma cell line U87 MG were treated with 1 μM of GHRH antagonist MIA-690 bound to GMO-MENs in MEM media supplemented with 5% FBS and 1% penstrep. In parallel, an in vitro BBB experiment, designed using transwells, applied a D.C. magnetic field gradient to determine optimal field and exposure time for MENs to penetrate the BBB. Next, experimental cells were placed on a D.C. magnetic field (100 Oe) for 12 h to induce nanoelectroporation, then an A.C. field (∼50 Hz) for 2 h to release the peptide intracellularly. Control cells were treated with MIA-690 peptide only, GMO-MENs only, and MIA-690 bound to GMO-MENs at varying magnetic fields and exposure times. Cells were incubated at 37°C with 5% CO2 in a humidified atmosphere. At 24 h and 48 h post-treatment, trypan-blue vital stain assessed cell growth inhibition. Cells were then washed and lysed to measure the concentration of MENs, and MIA-690 using ICP-MS and spectrophotometry, respectively. AFM and SEM-EDS imaged MENs in cell lysate and brain tissue from mice IV injected with MENs, to find signature peaks of Ba and Ti representing the outer core of MENs, to ascertain if particles cross the BBB in vivo. Summary of data: Glioblastoma cells treated with MIA-690 bound to GMO-MENs on a D.C. magnetic field for 12 h, then an A.C. field for 2 h exhibited the greatest penetration of MENs and inhibition of tumor growth. AFM and SEM-EDS imaging showed MENs in cell lysate treated with D.C. for 12 h, but not 2 h or with no magnetic field, confirming application of a low D.C. field for 12 h triggers MENs’ penetration. On-demand MIA-690 intracellular release was highest after exposure to 12 h of D.C. field, then A.C. field at 50 Hz. Confocal microscopy confirmed a transfer of at least 50% of drug-loaded MENs across in vitro BBB, requiring 200 Oe/cm for 5 h. SEM-EDS images of brain slices taken from mice treated with MENs confirmed the presence of Ba and Ti, indicating MENs are able to cross BBB in vivo. Conclusion: Functionalized MENs are effective in treating glioblastomas using targeted, on-demand release of anti-tumor drug with the ability to cross the BBB. Citation Format: Tiffanie Stewart, Emmanuel Stimphil, Rakesh Guduru, Alexandra Rodzinski, Ping Liang, Carolyn Runowicz, Ren-Zhi Cai, Luis Salgueiro, Andrew Schally, Sakhrat Khizroev. Magnetoelectric particles cross blood brain barrier to deliver anti-tumor peptide to glioblastoma cells with on-demand release. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1346.

Most cancer therapy is nonspecific, aimed at all dividing cells, resulting in untoward side effects. Our study demonstrates the effectiveness of magnetoelectric nanoparticles (MENs), which have been developed to address the critical issue of normal cell off-targeting in cancer treatment, in both in-vitro and in-vivo studies, as well as characterizes their biodistribution and clearance. Exploiting the difference in electric properties between normal and cancer cell membranes, MENs are able to enter cancerous cells carrying a therapeutic payload and release the payload intracellularly with the application of an external magnetic field, while not affecting normal cells. SKOV-3 human ovarian carcinoma cells were used as a model to showcase the unique cancer targeting capabilities of these CoFe2O4@BaTiO3 nanostructures coated with the mitotic inhibitor Paclitaxel (PTX). The MENs-PTX bond was characterized in the lysate of treated cells using spectroscopic analysis and scanning probe microscopy. SKOV-3 xenografted athymic nude mice were treated via subcutaneous or IV injection on a weekly basis with a MEN, conventional ferromagnetic nanoparticle (MN), or polymer nanoparticle (PLGA) formulation. Biodistribution and clearance of MENs is one of the most important open questions addressed in this study. Our approach is to investigate the key parameters that affect the therapeutic index, i.e. the maximum tolerated dose, blood circulation half-life and biodistribution due organ accumulation. The approach is to study factors such as the size and shape of MENs, chemical composition, targeting ligand functionalization, MENs’ biodegradability, and microenvironment and other biological barriers. Besides using conventional fluorescent markers, a novel nanoparticle distribution approach based on energy-dispersion spectroscopy (EDS) is exploited. In-vitro studies on the cell lysate of MENs treated SKOV-3 cells determined reliable entry into the cells by MENs with the application of a small magnetic field (∼100 Oe) and reliable payload release with the application of an a.c. magnetic field (∼50 Oe, 100 Hz). In-vivo studies demonstrated that the MENs-PTX formulation in combination with an externally applied magnetic field reduces tumor growth rate when injected subcutaneously, and fully cures the cancer when delivered via IV-injection. The MENs formulation was more successful in treating the tumor than both MN and PLGA formulations. EDS confirmed the presence of MENs in tumor tissues. MENs provide a novel mechanism by which cancer cells are targeted (using the difference in the cancer electric cell membrane properties compared to normal cells) and a drug payload is released (externally triggered with the application of an a.c. magnetic field) reliably. The underlying physics of the electric field interactions involved in the MENs drug delivery system was demonstrated here using ovarian cancer, but can be applied to virtually any cancer. Citation Format: Alexandra Rodzinski, Rakesh Guduru, Emmanuel Stimphil, Tiffanie Stewart, Ping Liang, Carolyn Runowicz, Sakhrat Khizroev. Targeted, controlled anticancer drug delivery and release with magnetoelectric nanoparticles. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2204.

Magnetic hysteresis measurements are performed on single crystals of Tl 2 Ba 2 CuO 6+δ superconductors with field parallel to the ab -plane. Our results show anomalously the Bean type critical state behavior with constant critical current in this orientation. The penetration field H p ( T ) depends on temperature T according to H p = H p (0) [1 − (T/T c ) 2 , in sharp contrast to H p (T) with field in the axis c -axis direction. For samples with high transition temperatures, the magnetization undergoes abrupt changes as a function of field at low temperatures. We propose that pinnings on the Josephson vortices in this direction are due to structure defects in these crystals. A local variation in the tunneling distance will introduce a finite pinning on Josephson vortices moving along the ab -plane. The abrupt change in magnetization may be due to field induced decoupling of the Josephson interaction between the layers.

Background: An important challenge in chemotherapy is targeted drug delivery to eradicate tumor cells while sparing normal cells. The circulatory system can deliver a drug to almost every cell in the body; however, delivering the drug specifically into the tumor cell and then releasing it on demand remains a formidable task. Nanoparticles posses unique properties to address this issue. Despite their great potential, a significant problem remains to ensure that the drug is not prematurely released in the plasma or interstitial space but is released at an appropriate rate once at the target site. Recently, we discovered a new class of “smart” multifunctional nanostructures known as magnetoelectric nanoparticles (MENs) that enables a high-efficacy “communication” between intrinsic electric fields at the intra-cellular level, which are inherent to the cellular membrane nature, and external magnetic fields, to control targeted drug delivery and release into specific tumor cells on demand. Herein, the results of a comprehensive in vitro study and an in vivo study on using MENs to treat ovarian cancer (OC) are presented. Methods: A specific combination of d.c. and a.c.-magnetic fields is used to externally control and separate delivery and release functions, respectively. MENs in a wide diameter range, 5-1000nm, are made of coreshell CoFe2O4@BaTiO3 nanostructures. The novel approach is compared to current state-of-the-art nanotechnology deliveries including (i) active immunochemotherapeutic approaches using polymer nanoparticles conjugated with monoclonal antibodies (mAbs) and (ii) passive enhanced permeability and retention (EPR)-based approach using polymer nanoparticles without any immunoactive reagents. Mitotic inhibitor paclitaxel (PTX)–loaded MENs are administrated through systemic IV injection into a lateral tail vein or through localized subcutaneous injection directly into the tumor site. The tumor progression is monitored through infrared (IR) imaging witth mAb-conjugated fluorescent agent Her2Sense 645. Post euthanasia, the cell morphology and the tumor presence in different organs are further studied with H&E stain and Her2Sense agent, respectively. The biodistribution of the nanoparticles in the tumor sites and different organs of mice treated under different field conditions are studied through the energy-dispersive spectroscopy (EDS) mode of high-resolution scanning electron microscopy (SEM). Finally, after the completion of the treatment, the cured mice are monitored for a period of three months before being sacrificed for further immunohistochemical and particle biodistribution studies. Results: Using MENs loaded with PTX, the in vivo study on nude mice bearing SKOV-3 human ovarian carcinoma xenografts shows that intravenously administrated MENs enable high-specificity delivery and release via application of d.c. and a.c. magnetic fields, respectively. MENs distinguish cancer cells from the normal counterparts by the difference in the membrane’s electric properties. The control mice are treated with PTX loaded on ferromagnetic and polymer nanoparticles conjugated with HER2-neu antibodies. Only the mice which are weekly treated for three months with PTX-loaded 30-nm MENs (15/200 µg) in a 100-Oe local field are completely cured, as confirmed through infrared imaging and post-euthanasia immunohistochemical analysis. A comparison between systemic IV and localized subcutaneous injections of PTX-loaded MENs show that although both delivery approaches significantly slow down the progression of the tumor, the IV administration is more efficient and, unlike the subcutaneous administration, can completely eradicate the tumor during the three-month treatment period. An important observation from this study is the strong dependence of the amount of MENs in the tumor site and all the organs of treated and control mice on the external magnetic field control. The same conclusion was drawn also from the comprehensive in vitro study, in which the detailed cell lysate content was measured using direct AFM/MFM imaging of MENs and spectrophotometry detection of the drug under the investigated field conditions. Conclusion: In summary, the study directly shows that the drug-loaded MENs provide a novel way to deliver the drug specifically into the tumor site via application of a d.c. field and then, when at the site, the drug is released directly inside the cancer cells via application of an a.c. field. Citation Format: Alexandra Rodzinski, Ali Hadjikhani, Tiffanie Stewart, Emmanuel Stimphil, Rakesh Guduru, Ping Liang, Carolyn Runowicz, Sakhrat Khizroev. A novel mechanism for field-controlled high-specificity targeted anticancer drug delivery and on-demand release using magnetoelectric nanoparticles. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr B47.

Despite theoretical predictions, the question of room-temperature magnetic order in graphene must be conclusively resolved before graphene can fully achieve its potential as a spintronic medium. Through scanning tunneling microscopy (STM) and point I-V measurements, the current study reveals that unlike pristine samples, graphene nanostructures, when functionalized with aryl radicals, can sustain magnetic order. STM images show 1-D and 2-D periodic super-lattices originating from the functionalization of a single sub-lattice of the bipartite graphene structure. Field-dependent super-lattices in 3-nm wide "zigzag" nanoribbons indicate local moments with parallel and anti-parallel ordering along and across the edges, respectively. Anti-parallel ordering is observed in 2-D segments with sizes of over 20 nm. The field dependence of STM images and point I-V curves indicates a spin polarized local density of states (LDOS), an out-of-plane anisotropy field of less than 10 Oe, and an exchange coupling field of 100 Oe at room temperature.

International audience; The authors report the effects of radical functionalization on the electrostatic force microscopy (EFM), the scanning tunneling spectra (STS), and Raman spectroscopy of epitaxial graphene. The EFM studies show the existence of layer dependent trapped charges in the pristine graphene. The uniform enhancement of energy gap is observed through STS. Raman spectra show nonuniformly distributed D-band intensities throughout the functionalized sample as a result of the inhomogeneous distribution of covalent bonds to the graphene sheets. The functionalization chemistry has a marked effect on the homogeneity of the electrostatic charge and leads to an increase of the energy of the band gap.

There is an error in the title of the article. The correct title is: Carbon Nanotube Based 3-D Matrix for Enabling Three-Dimensional Nano-Magneto-Electronics. The correct citation is: Hong J, Stefanescu E, Liang P, Joshi N, Xue S, et al. (2012) Carbon Nanotube Based 3-D Matrix for Enabling Three-Dimensional Nano-Magneto-Electronics. PLoS ONE 7(7): e40554. doi:10.1371/journal.pone.0040554

A focused ion beam process was utilized to physically define a “point dipole” magnetic force microscopy (MFM) tip with cylindrical dimensions as small as 50 nm in diameter and 10 nm in height. By controlling the preferred orientation of the magnetization, it is possible to define directional sensitivity. The preferred orientation is controlled either by choosing a proper magnetic material with preferred crystalline anisotropy or by applying a sufficiently strong external magnetic field. The signal selectivity with respect to the imaged field orientation allows more direct information to be obtained from the imaged object, as compared to the information obtained from the same object when using a conventional MFM tip.

This work addresses the recording physics of narrow-gap single-pole heads (SPH) in perpendicular recording. It is found that narrow-gap SPHs have reduced sensitivity with respect to nonzero skew angles. It is shown that while the efficiency of a narrow-gap SPH is generally reduced, even for the case of a gapless SPH, the efficiency differs from the efficiency of a 1-/spl mu/m-thick gap SPH only by a factor of two. The design parameter space for a narrow-gap SPH is investigated.

Summary form only given. A perpendicular medium with a soft underlayer (SUL) combined with a single pole head (SPH) is believed to be the most suitable system configuration for successful implementation of perpendicular recording. The influence of a SUL on the dynamic characteristics of a recording system is one of the key issues pertinent to the development of the technology. A detailed study of the SPH/SUL dynamics was conducted by D. Litvinov et al (IEEE Trans. Magn., vol. 37, no. 4, p. 1376, 2001). The present work extends this analysis to include the influence of a recording layer (RL) on the SUL dynamic characteristics.

Summary form only given. In a typical perpendicular system, writing is done by the trailing edge of the trailing pole (TP) of a single pole head (SPH). The recording field is controlled by the electrical current in a magnetizing coil. However, due to the use of a soft underlayer (SUL) there is an additional source of the magnetic flux, which indirectly contributes to the net recording field under the TP. Due to the multiple magnetic image reflection (MIR) effect, the magnetic flux can be extracted from the recording layer (RL) region under the leading pole (LP) and transferred to the region under the TP. It should be stressed that a DC-erased perpendicular medium in the presence of only one or no "mirrors" generates no stray field at all. The fact that a field of approximately 1.4 kOe can be extracted from a DC-erased medium, indicates that the MIR is clearly a multiplication process, in which the LP and SUL act as two magnetic "mirrors" that effectively displace the magnetic charges from the surfaces of the recording layer to "infinity." The intention of this paper is to theoretically and experimentally study in detail the consequences of the MIR on the recording characteristics of a recording system.

Using a 3D expression for the stray field emanating from a perpendicular medium with information recorded at different areal densities, the effects of the magnetic ?charge? distribution were explored. The existence of a peak in a density roll-off curve is one of the typically observed effects in perpendicular recording. Comparison between longitudinal and perpendicular recording technologies was made, and guidelines helping appropriately choose the bit aspect ratio (BAR), the recording layer thicknesses, and other parameters, were derived.

The goal of any surgery is the patient's complete recovery with maximum relief and minimal adverse effects. This goal is less complicated when epilepsy is predicated on tumor location revealed through standard imaging studies, in which case noninvasive post surgical studies can relate the 3D source with the area of the tumor that was removed. Success is more difficult, however, in non-lesional cases, where the characteristics of the epilepsy event are more difficult to define. This challenge reinforces the need for accurate 3D source localization to guarantee success of the first surgical intervention. Through this major undertaking which integrates recording modalities in time and space, clinicians and surgeons become more confident at prescribing a resection, especially when markers for the epileptogenic area and related brain functional assessments are consistent with the area thought to be the cause of the diagnosed neurological problem. This study evaluates the utility of 3D localization of interictal spike activity on the electroencephalographs (EEG) superimposed on magnetic resonance imagery (MRI) in a pediatric population. The results show a 99% concordance between EEG source localization and the suggested epileptogenic zone

The effects of substrate Ar-ion milling and Ta adhesion layer on the microstructural and magnetic properties of L1(0)-FePt films prepared on Si, SiO2, and glass substrates were investigated. It was discovered that the relatively large in-plane surface roughness of CrRu/MgO/FePt films deposited on Si substrates was due to the deformation of the CrRu layer when the composition was heated to 550 degrees C. More than an order of magnitude improvement for the in-plane surface roughness was achieved when substrate Ar-ion milling or Ta adhesion layer was incorporated into the process. While the Ta adhesion layer proved to be detrimental to the (200) growth of the CrRu layer, optimal FePt film properties with coercivity values larger than 2 Tesla and out-of-plane roughness less than 1 nm were achieved when only substrate Ar-ion milling was implemented.

This work addresses the issue of cubic phase formation in boron nitride thin-film systems. The presented data suggest strain-induced formation of cubic phase. The compliant nature of the turbostratic boron nitride buffer layer is shown to be an essential factor for cubic phase nucleation. Two distinct regimes of cubic phase formation are observed. First, a cubic boron nitride seed layer is formed on top of the turbostratic boron nitride buffer layer under nitrogen ion irradiation of the growth surface. This is followed by the growth mode of the cubic phase, which requires a different set of growth conditions. The role of nitrogen ion irradiation in two deposition regimes is discussed.

We have investigated Co/Pd multilayers deposited on either Ta or indium tin oxide (ITO) seed layers as a potential perpendicular recording media. We have examined the microstructural evolution of the films deposited on the two different types of seed layers and related it to the magnetic properties of the films. Ta underlayer produces a strong 〈111〉 fiber texture in the multilayer while ITO produces randomly oriented grains. Transmission electron microscopy reveals a microstructure of columnar grains separated by less dense material at the boundaries for the multilayers with an ITO underlayer. However, the less dense material is absent when using a Ta underlayer. The films exhibited strong perpendicular anisotropy and a higher coercivity of ∼6800 Oe and squareness of ∼0.99 are obtained for the films deposited on an ITO seed layer. The differences in the value of coercivity and squareness in the films can be correlated with the differences in the evolution of microstructures for different seed layers.

Application of reflection high-energy electron diffraction (RHEED) to texture determination is demonstrated for magnetic thin film applications. Diffraction pattern analysis based on kinematic theory of RHEED is outlined. Application of the technique is demonstrated for texture characterization of hexagonal-close-packed CoCr alloys that are used as recording layers in perpendicular recording media. It is shown that both texture orientation and texture angular dispersion extracted from RHEED patterns are in agreement with the data obtained using x-ray diffraction.

In single-pole heads with a pole tip cross section trimmed down to 1003200 nm by focused ion beam, the remanence of the head becomes nonzero if the pole length is too high. Large-scale three-dimensional micromagnetic simulations are performed to understand this effect, and to calculate the critical length of the pole as a function of the pole tip cross section.

Focused ion beam etching has been used to trim both longitudinal and perpendicular recording heads with track widths as narrow as 60 nm. 3D boundary element modeling has been used to optimize trimming parameters. Tracks written with the trimmed heads using spin-stands and imaged using magnetic force microscopy were as narrow as 100 nm.

We describe the fabrication of large-area magnetic ring structures using ion beam proximity lithography (IBPL) to pattern an array of circular openings and then use a conforming oxide coating to define the ring structure through the sidewall coating. Arrays of Permalloy rings with sub 500 nm outer diameter and 150 nm inner diameter on a 650 nm pitch over a 5.5 mm times 6 mm area were fabricated to study transitions between the micromagnetic configurations within these structures. The results suggest that the field required for onion-to-vortex transition and field required for vortex-to-onion transition to be 0Oe and 400Oe, respectively.

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. IBPL is used to reduce the size distribution sigmaD of the arrays, and subsequently He+ ion irradiation is used to reduce their anisotropy. 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. We argue that the slope of the line is due to the self-demagnetization effect of individual dots (and therefore, it is not strictly a line) and that the intercept of the line is inversely proportional to the permeability of the nanostructured material.

We present the results of micromagnetic studies on stability and bit propagation in the patterned nanodot chains. In particular, we discuss periodic results of long-array switching using a clocking field.

Domain wall dynamics in magnetic nanodots is critical to the understanding of the magnetization reversal mechanisms in bit-patterned arrays, the issues of writeablility, data rate maximization, and bit stability. In this work, micromagnetic simulations were carried out to investigate the dynamics of domain walls in disk-shaped nanostructures with large built-in perpendicular anisotropy. Due to the strong demagnetizing effect, the domain wall motion falls into the supercritical regime. A 90 degrees phase shift of the wall velocity is developed due to the finite thicknesses. The mean value of the wall velocity increases as the domain wall propagates away from the center. This induced asymmetry causes the frequency of the wall oscillations to be halved. At large diameters, the wall acceleration deceases and the periodicity is lost. The in-plane magnetization configuration shows that multiple spin wave modes are present. The absence of the coherency in the magnetization orientations causes phase canceling. The out-of-phase motion of neighboring segments reduces the wall acceleration.

Well crystalline cobalt ferrite CoFe2O4 nanoparticles (50-100 nm) were produced using carbon combustion synthesis of oxides (CCSO). In this process the exothermic oxidation of carbon generates a thermal reaction wave that propagates at a velocity of 0.1-3 mm/s through the solid reactant mixture of cobalt and iron oxides converting it to the cobalt ferrite without any external power consumption. This will enable a reduction in the production price of cobalt ferrite by minimization of the energy consumption. The combustion temperature can be set by proper choice of the amount of carbon added to the mixture of solid reactants. The extensive emission of CO2 enhanced the porosity and friability of product. The as-synthesized ferrites had hard magnetic properties with coercivity 700 Oe and saturation magnetization up to 47 emu/g.

We describe the lithographic structuring of large-area patterned medium samples with sub-50 nm features using ion beam proximity lithography (IBPL). The quality of the patterns formed in IBPL system is primarily limited by the quality of the stencil masks. Hence, the emphasis of this work has been to develop a reliable mask fabrication process that can achieve a size uniformity that is suitable for patterned media. We have developed a mask fabrication approach that incorporates palladium as a hard mask for transferring the lithography pattern through a silicon nitride membrane. A conformal gold coating allows for further reduction of the mask features without a significant increase in the feature size variation. An average standard deviation of 3 nm and 5 nm was measured during various steps of the stencil mask fabrication and after printing using IBPL in PMMA resist, respectively. Patterned medium prototypes with features ranging from 40 nm to 300 nm have been fabricated and magnetic properties measured. A 6-12 fold increase in coercivity was measured for multilayer samples after patterning. Ion irradiation of patterned multilayer samples was also studied as a means to control magnetic anisotropy as well as to evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. Patterned multilayer samples show a decrease in coercivity from 11 kOe for as-patterned to 0.3 kOe for 800 muC/cm2 and suggests that ion irradiation can be an integral part of bit patterned medium fabrication for anisotropy control.

Design considerations and fabrication of bit-patterned magnetic recording media are presented. The application of ion-beam proximity printing, a high-throughput direct-write lithography, to media patterning is evaluated. Ultra-high magnetic anisotropy (Co/Pd)N magnetic multilayers are analyzed as candidates for patterned recording layers. Following patterning, optimized multilayers are shown to exhibit coercivity values well in excess of 14kOe. It is found that the magnetization reversal in patterned bits takes place via domain wall nucleation and propagation. The nucleation field and the location of the nucleation site strongly depend on the bit edge imperfections and contribute to finite switching field distribution. Playback off a bit-patterned media using various magnetic reader designs is analyzed using reciprocity theory.

We present the results of micromagnetic studies on realistic patterning defects in perpendicularly oriented magnetic thin films. Both undercut and line edge roughness are investigated systematically with simulations using simple test structures to see the effect of the side wall angle, the roughness amplitude on a nanostructureiquests switching field, and the roughness period on mathematically tractable figures. We then run simulations of hysteresis loops of actual 200 nm diameter nanostructures using AFM images to define the structure boundary and compare the results to MFM images of DC demagnetized dots.

The perpendicular fields emanating from an ultra small perpendicular single pole heads have been quantified using a new MFM field mapping technique. This technique utilizes two MFM tips with different field sensitivities which have been focused ion beam etched to identical geometries. This technique has been used to quantify the perpendicular fields around a 100/spl times/200 nm pole, also fabricated with focused ion beam etching.

This paper will present an unconventional way to answer the above questions. In contrast to the conventional flat geometry of SUL, it is proposed to use a patterned SUL. FEM-based simulations will be performed to illustrate many key benefits of the use of a patterned SUL.

This work presents an annealing study of high-anisotropy (Co/Pd)N magnetic multilayers designed for bit-patterned medium recording applications. Magnetic multilayers were deposited by magnetron sputtering at 2.5mT argon pressure at room temperature and annealed at different temperatures (up to 250 °C) for up to 2 hours in atmosphere and in vacuum. Depending on the annealing time, the samples annealed in atmosphere exhibited two distinct modes of magnetization reversal. In samples annealed for a time shorter than some critical time, tc, where tc is a function of the annealing temperature, the magnetization reversal occurs by domain wall injection and propagation. In samples annealed for times longer then tc, the magnetization reversal mode switches to magnetization rotation. Using XPS, it is found that the transition is accompanied by the formation of oxidizes at the grain boundaries leading to exchange decoupling of the grains. In samples annealed at higher temperatures, the increases of the coercivity of as high as 30 times the coercivity of as prepared samples are observed. Significantly, annealing in vacuum showed only small modification of magnetic properties as manifested by relatively minor modifications of vertical M-H loops and unchanged morphology of domain patterns in AC demagnetized state.

We have been pursuing protein-based memory using genetically altered bacteriorhodopsin (bR) and exploring limits of high density optical recording using far-field and near-field approach. bR was immobilized on very thin LB films

Thin film perpendicular playback yoke-GMR heads capable of reading at a density of 100 Gbit/in/sup 2/ have been designed using 3D boundary element reciprocity modeling. Two basic head types are considered, a single-pole and a ring-type geometry. The influence on the playback voltage and D/sub 50/ of the throat height, fly height, and permeability are studied. Isolated pulse response, roll-off curves, and off-track profiles are calculated. Media with and without a soft underlayer are also considered. The simulations show that of the designs studied the ring head in combination with the media without a soft underlayer has playback properties suitable for this density.

In the course of this proposal, it is proposed to develop and simulate a thermally-stable one-thousand-layer 3-D recording system with an eight-bit address/word line capable of recording and retrieving eight bits in parallel. Assuming a bit cell with one square micron in cross-section, this is equivalent to an effective areal density of 640 Gbit/in2. The undergraduate student involved in this proposal (Nissim Amos) and the PI will make a presentation of the results of the numerical simulations indicating the functionality of the device. The simulations proposed will be performed both with PC and a state-of-the-art computer cluster system recently established at FIU. The use of the cluster computing will allow to extend the simulations (in the near future) to systems capable of pentabyte recording. The simulations will incorporate both magnetostatic and micromagnetic (quantum-mechanical) interactions between the grains in the 3-D media. The thermal stability of the recording media will be addressed throughout the simulations. In the course of this proposal, it is planned to raise interest in this technology at least to the level of prototype building. A detailed plan (with drawings and steps) to build a first-principle prototype will be proposed by the end of the project. In the course of this proposal, it is planned to publish at least two articles (one on the modeling technique and the other on the simulation results) in peer-review journals (upon an agreement with US Air Force). The above-described project on simulation of a 3-D magnetic recording system will be conducted in parallel with the experimental work on the prototype development.

The inaugural conference on Nanoscale Devices and System Integration (NDSI-2004) was held in Miami, Florida, 15-19 February, 2004. The focus of the conference was `real-life' devices and systems that have recently emerged as a result of various nanotechnology initiatives in chemistry and chemical engineering, physics, electrical engineering, materials science and engineering, biomedical engineering, computer science, robotics, and environmental science. The conference had a single session all-invited speaker format, with the presenters making the `Who's Who in Nanotechnology' list. Contributed work was showcased at a special poster session. The conference, sponsored by the Institute of Electrical and Electronics Engineers (IEEE) and the US Air Force, and endorsed by Materials Research Society (MRS), drew more than 160 participants from fourteen countries. To strengthen the connection between fundamental research and `real-life' applications, the conference featured a large number of presenters from both academia and industry. Among the participating companies were NEC, IBM, Toshiba, AMD, Samsung, Seagate, and Veeco. Nanotechnology has triggered a new wave of research collaborations between researchers from academia and industry with a broad range of specializations. Such a global approach has resulted in a number of breakthrough accomplishments. One of the main goals of this conference was to identify these accomplishments and put the novel technology initiatives and the emerging research teams on the map. Among the key nanotechnology applications demonstrated at NDSI-2004 were carbon-nanotube-based transistors, quantum computing systems, nanophotonic devices, single-molecule electronic devices and biological magnetic sources. Due to the unprecedented success of the conference, the organizing committee of NDSI has unanimously chosen to turn NDSI into an annual international nanotechnology event. The next NDSI is scheduled for 4-6 April, 2005, in Houston, Texas. Details can be found on the conference web site at http://www.nanointernational.org. This special issue of Nanotechnology features selected papers from NDSI-2004.

Today, one of the most critical issues in implementing perpendicular recording is believed to be the excessive sensitivity of a typical perpendicular recording system to the skew angle. In perpendicular data storage, the recording is expected to be produced in the effective gap near the trailing edge of the main pole of a single pole head (SPH). In this paper, magnetic force microscopy (MFM) is utilized to study the skew angle effects in perpendicular media with a CoCr-based hard layer and a Permalloy soft underlayer.

Summary form only given. The nature of the stray and demagnetizing field in perpendicular media is drastically different from what is observed in conventional longitudinal recording. In contrast to longitudinal recording, in perpendicular recording the magnetic "charges," which are the effective sources of the demagnetization and stray fields, are concentrated not at the transitions but at the top and effective bottom surfaces of the recording layer (RL). Based on analytical calculations and 3D-boundary element modeling a detailed analysis of the stray and demagnetization fields for perpendicular RL as functions of the areal bit density, the bit-aspect-ratio (BAR), linear and track densities, and the RL thickness is presented. The observed dependencies are contrasted to dependencies observed in longitudinal recording.

Summary form only given. Perpendicular recording is believed to be one of the most promising candidates for the future generations of hard drives, because perpendicular recording is technically close to conventional longitudinal recording while it addresses the critical issue of thermal stability. A magnetic force microscopy (MFM) study of the data stability in a double-layer perpendicular magnetic recording medium is presented. Autocorrelation signal-to-noise ratio (ACSN) and more conventional signal-to-noise ratio (SNR) analysis were used in conjunction with MFM to characterize the integral noise characteristics of the written tracks. Transition noise, DC noise, and percolation effects were also studied to provide more detailed information on various sources of noise. Two types of media were investigated: CoCr-alloy based with relatively low remanent squareness of 0.7 and coercivity of 3.5 kOe and a Co/Pd based multilayer with remanent squareness of 1, coercivity field of 7 kOe and nucleation field of 3 kOe.

In this paper, we discuss the concept and prototype fabrication of reconfigurable and non-volatile vertical magnetic logic gates. These gates consist of two input layers and a RESET layer. The RESET layer allows the structure to be used as either an AND or an OR gate, depending on its magnetization state. To prove this concept, the gates were fabricated using a multi-layered patterned magnetic media, in which three magnetic layers are stacked and exchange-decoupled via non-magnetic interlayers. We demonstrate the functionality of these logic gates by conducting atomic force microscopy and magnetic force microscopy (MFM) analysis of the multi-layered patterned magnetic media. The logic gates operation mechanism and fabrication feasibility are both validated by the MFM imaging results.

3D modeling and inductance measurements were used to design an ultra-high frequency perpendicular system. Kerr microscopy and spin-stand experiments with focused ion beam (FI-B) trimmed perpendicular heads and perpendicular media directly verified the high frequency concepts.

The results of the experimental study of CoX/Pd multilayer based recording layers for perpendicular recording media are presented. The perpendicular magnetic recording media with multilayer recording layers and high moment soft underlayers were deposited by magnetron sputtering. It is shown how a favorable microstructure of the multilayer films can be achieved by the use of the appropriate buffer layers. The effects of boron addition to the cobalt layer in a multilayer recording layer is described. The feasibility of the aging process that leads to the reduced exchange coupling in the multilayer recording layer, is demonstrated. It is shown that boron addition to the cobalt layer accelerates the aging process.

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005

We compute the switching field in a disk-shaped polycrystalline exchange-coupled bit (similar material to those found in bit-patterned media (BPM)) with micromagnetics, by varying physical parameters of a test grain. It was found that the size and the anisotropy of the test grain have substantial effects on the switching field, while its location has only minor influence. Scaling of the bit and the test grain dimensions result in similar switching properties. Switching field was reduced when the number of the low anisotropy test grains increased. Additionally, it was established that the intergranular exchange coupling needs to be at least 10% of the intragrain exchange for the bit to behave as one exchange-coupled entity. This investigation provides some insights for optimizing the material microstructure for the BPM application.