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In this work, we present a detailed investigation of the magnetic properties of cobalt nanospheres grown on cantilever tips by focused electron beam induced deposition (FEBID). The cantilevers are extremely soft and the cobalt nanospheres are optimized for magnetic resonance force microscopy (MRFM) experiments, which implies that the cobalt nanospheres must be as small as possible while bearing high saturation magnetization. It was found that the cobalt content and the corresponding saturation magnetization of the nanospheres decrease for nanosphere diameters less than 300 nm. Electron holography measurements show the formation of a magnetic vortex state in remanence, which nicely agrees with magnetic hysteresis loops performed by local magnetometry showing negligible remanent magnetization. As investigated by local magnetometry, optimal behavior for high-resolution MRFM has been found for cobalt nanospheres with a diameter of ≈200 nm, which present atomic cobalt content of ≈83 atom % and saturation magnetization of 106 A/m, around 70% of the bulk value. These results represent the first comprehensive investigation of the magnetic properties of cobalt nanospheres grown by FEBID for application in MRFM.

Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution.

Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution.

We describe the accomplishments of the collaborative research project performed at Ohio State University (OSU) and the University of Illinois at Urbana-Champaign (UIUC) with the support of ARO MURI grant W911NF-05-1-0414 between August 1, 2004 and July 31, 2009. Frequent interactions with Dan Rugar (IBM Almaden) have contributed significantly to our research. Our primary goal-single nuclear spin Magnetic Resonance Force Microscopy (MRFM)-calls for ultrasensitive detection as signal forces will be below 1 aN. We report several foundational accomplishments central to the achievement of this extraordinary sensitivity and development of methods for applying this technique to scientifically and technologically important problems. The primary milestones include but are not limited to: 1. Mitigation of sample-induced noise to enable sensitive ESR-MRFM detection of 2.3 electron spins in a 0.20 Hz bandwidth 2. Application of ultra-sensitive ESR-MRFM to the study of electron spin relaxation in spin ensembles containing of order 100 electron spins 3. Advances in development and characterization of semiconducting (Si) nanowires as next-generation ultrasensitive force detectors 4. Demonstration of high sensitivity Cu NMR measurements in technologically important layered metallic systems We have transferred expertise and technology for high sensitivity scanned probe magnetic resonance detection to DOD and DOE labs needing state-of-the-art spin imaging capabilities; these include the Naval Research Lab (NRL) and Los Alamos National Lab. In work not directly supported by this grant, these projects advanced MRFM detected Ferromagnetic Resonance (FMR) to enable studies of submicron magnetic structures having relevance to magnetoelectronics, magnetic field sensors and the magnetic data storage., Prepared in cooperation with University of Illinois at Urbana-Champaign. The original document contains color images.

This report describes a software package that was written to support the U.S. Army Research Laboratory's (ARL) program in force-detected nano-magnetic resonance imaging (MRI). The software characterizes the noise found in cantilevers used for nano-MRI. The noise can be thermal noise that manifests itself as the Brownian motion of the cantilever, or it can be environmentally induced from external forces that excite the cantilever. The program analyzes the noise of both undriven and driven cantilevers. The program determines the root mean square (RMS) value of the undriven cantilever's motion versus time and its displacement power spectrum. The driven cantilever will experience instantaneous frequency deviations from the driving frequency due to Brownian motion. This program determines the instantaneous frequency of the cantilever and calculates the mean, standard deviation, and frequency deviation power spectrum of the cantilever's frequency versus time. Although developed to characterize the noise in a cantilever, the analysis preformed here is valid for characterizing the noise on a carrier independent of the source of the carrier and its noise., The original document contains color images.

This program intended to provide substantial improvements to conditions that affect imaging nanoscale structures with atomic resolution and chemical specificity by magnetic resonance force microscopy. This is a final report of an 18 months effort. During this period we the following activities: We increased the sensitivity of the cantilever displacement readout and therefore the force sensitivity achievable with mechanical detection. We implemented an approach to reduce the spin noise in MRFM by shifting to higher frequencies the higher order cantilever vibrational modes. We build a low temperature microscope that operates in vacuum at 4K in a field of up to 9Tesla and tested the system. Finally, we selected CaF2 as the first sample to test the feasibility of performing magnetic resonance force spectroscopy within the resonance slice, prepared samples and characterized the sample.

We proposed to complete three tasks in this project. These tasks were MRFM imaging with nanometer-scale resolution end-to-end performance analysis of quantum spin imaging and a reference design for a year-20O6 quantum microscope. At the time of this report, nanometer-scale MRFM imaging has been achieved at 8Onm resolution. A performance analysis was completed, and published as an invited paper in the Proceedings of the IEEE on the Classical and Quantum Theory of Thermal Magnetic Noise. With recent work in spin simulation exactly matching recent experiments performed at IBM, this technical report represents the deliverable of a complete Reference Design and Performance Analysis (RDPA) as originally proposed., The original document contains color images.

This report covers work performed on two-dimensional and three-dimensional reconstruction of magnetic images derived from synthetic data sets of a model magnetic-resonance force microscope. Specifically, Pixon LLC has employed its proprietary Pixon-method image reconstruction algorithm to perform the reconstructions. The authors find that the algorithm yields excellent results, particularly with regard to image accuracy, resolution, and suppression of noise. A specific and robust regimen for performing the reconstructions within the Pixon-method paradigm was developed. The regimen is robust against varying signal-to-noise ratio and varying tip-to-sample separation in the MRFM instrument model. Moreover, a data-capture scanning strategy has been discovered that optimizes performance of the reconstruction (resolution and sensitivity) while simultaneously minimizing the data acquisition time. These results should make the application of the algorithm in a real-world instrument straightforward. The results also favor adaptation of Pixon-method image reconstruction techniques to three-dimensional imaging with conventional magnetic-force microscopes.

Key technologies required to bring the instrument to market with sensitivity to a few thousand protons were demonstrated including a novel cryogenic coarse approach mechanism and the first-ever batch fabrication of attoNewton-sensitive "ultrafloppy" cantilevers with individual nanomagnets on the tips. A prototype digital-signal-processor (DSP) based cantilever controller suitable for use in an MRFM instrument was developed. It is a significant accomplishment to be able to employ a DSP in a scanned probe microscope measurement. We have determined that this technology is suitable for optimization and manufacture of a commercial microscope, with initial applications in thin-film materials analysis. Eventual broad commercial and military applications will benefit from this technology including: research of advanced materials, advanced semiconductor-device research (e.g. individual impurity and defect characterization, assaying spin injection in spintronics devices), single-molecule analytical chemistry, infectious disease research, biotechnology, nanoelectronics, and new solid-state physics research., Prepared in cooperation with CRYO Industries of America, Manchester, NH; SC Solutions, Sunnyvale, CA. Topic no. Army 02-T010.

The quantum theory of a single-spin measurement using magnetic resonance force microscopy is presented. We use an oscillating cantilever-driven adiabatic reversal technique. The frequency shift of the cantilever vibrations is estimated. We show that the frequency shift causes the formation of a Schrodinger cat state for the cantilever. The interaction between the cantilever and the environment quickly destroys the coherence between the two cantilever trajectories. It is shown that using partial adiabatic reversals one can obtain a significant increase in the frequency shift. We discuss the possibility of sub-magneton spin density detection in molecules using magnetic resonance force microscopy., QC 20100525

We propose to use ferromagnetic resonance force microscopy to measure the dissipative term that enters in the equation of motion for the magnetization vector. The experiments were carried out at microwave frequencies on a micron-size single crystal disk of yttrium iron garnet. We compare the results obtained by resonance linewidth measurements and quantitative measurement of the longitudinal magnetization. © 2003 Elsevier B.V. All rights reserved.

We propose to use ferromagnetic resonance force microscopy to measure the dissipative term that enters in the equation of motion for the magnetization vector. The experiments were carried out at microwave frequencies on a micron-size single crystal disk of yttrium iron garnet. We compare the results obtained by resonance linewidth measurements and quantitative measurement of the longitudinal magnetization. © 2003 Elsevier B.V. All rights reserved.