Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session V9: Magnetic Force Microscopies |
Hide Abstracts |
Sponsoring Units: GIMS Chair: Albert Macrander, Argonne National Laboratory Room: Baltimore Convention Center 301 |
Thursday, March 16, 2006 11:15AM - 11:27AM |
V9.00001: Localized Spectroscopy using a Magnetic Resonance Force Microscope. Giorgio Moresi, Qiong Lin, Schahrazede Mouaziz, Andreas Hunkeler, Christian Degen, Urban Meier, Juerger Brugger, Beat Meier The Magnetic Resonance Force Microscope (MRFM) constitutes a promising next-generation magnetic resonance detection device at room temperature. A MRFM observes nuclear (or electron) spin magnetization as a force, which occurs when a paramagnetic sample is polarized in inhomogeneous static magnetic field (10E5 T/m) and a high frequency drives the cantilever on-resonance by a cyclic adiabatic modulation, which make able to measure T1 rho. In this contribution, we combine the MRFM with spin-echo spectroscopy to add spectral resolution to NMR signals of micro-scale objects at room temperature. First experimental spectra recorded with the amplitude detection technique from a sample of barium chlorate monohydrate and ammonium sulfate single crystals mounted on a non commercial cantilever show resolution of 2$\mu$m and a sensitivity of 10E13 spins. The new microscope, which uses the frequency detection down to m-Hz resolution and the annealed non-commercials cantilevers, which have Q factor up to 250000 at room temperature, improve the sensitivity to 10E9 spins. This new setup and a new measurement technique should make able to measure T1. [Preview Abstract] |
Thursday, March 16, 2006 11:27AM - 11:39AM |
V9.00002: High Sensitivity Magnetic Resonance Force Microscopy P. Banerjee, Y. Che, K.C. Fong, T. Mewes, V. Bhallamudi, Yu Obukhov, D.V. Pelekhov, P.C. Hammel We report high sensitivity detection of electron spin resonance from E$\,^\prime$ centers in fused silica using the Magnetic Resonance Force Microscope. Operating at low temperatures and with high magnetic field gradients in the 2--3 G/nm range, we easily observe magnetic resonance signals from less than 1000 $\mu_B$, and signal averaging enables detection of less than 100 $\mu_B$ with a spin sensitivity of 10 $\mu_B$. While $T_1$ at low temperatures is approximately 5 sec, the lifetime of the magnetization under conditions of periodic adiabatic reversal is considerably shorter and is observed to be of order 100 ms. We will discuss design features necessary to operate the microscope at millikelvin temperatures. [Preview Abstract] |
Thursday, March 16, 2006 11:39AM - 11:51AM |
V9.00003: Using High Coercivity Magnet Particle for High Sensitivity Magnetic Resonance Force Microscopy K.C. Fong, I.H. Lee, P. Banerjee, Y. Che, Yu. Obukhov, D.V. Pelekhov, P.C. Hammel We report on the application of a 40 micron diameter, high coercivity NdFeB magnetic particle for high sensitivity electron spin resonance detection using Magnetic Resonance Force Microscopy. The relatively large NdFeB magnetic particle allows us to obtain large field gradients at relatively large tip-sample separations which can reduce surface induced noise. Force signals due to two different spin manipulation protocols in high field gradient will be presented. Model of the forces generated by these excitation schemes provide insight, into the various spin manipulation techniques and the impact of magnetic particle size on high sensitivity spin detection. [Preview Abstract] |
Thursday, March 16, 2006 11:51AM - 12:03PM |
V9.00004: Experiments in Nuclear Magnetic Resonance Microscopy Yong Lee, Wei Lu, J.-H. Choi, H.J. Chia, U.M. Mirsaidov, S. Guchhait, A.D. Cambou, R. Cardenas, K. Park, J.T. Markert We report our group's effort in the construction of an 8-T, $^3 $He cryostat based nuclear magnetic resonance force microscope (NMRFM). The probe has two independent 3-D of piezoelectric x-y-z positioners for precise positioning of a fiber optic interferometer and a sample/gradient-producing magnet with respect to a micro-cantilever. The piezoelectric positioners have a very uniform controllable step size with virtually no backlash. A novel RF tuning circuit board design is implemented which allows us to simply swap out one RF component board with another for experiments involving different nuclear species. We successfully fabricated and are characterizing $50{\mu}m \times 50{\mu}m \times 0.2{\mu}m $ double torsional oscillators. We have also been characterizing ultrasoft cantilevers whose spring constant is on the order of $10^{-4}$ N/m. We also report NMRFM data for ammonium dihydrogen phosphate(ADP) at room temperature using our 1.2-T system. Observed features include the correct shift of the NMR peak with carrier frequency, increases in signal amplitude with both RF field strength and frequency modulation amplitude, and signal oscillation (spin nutation) as a function of tipping RF pulse length. Experiments in progress on NH$_4$MgF$_3$ (at 1.2 T) and MgB$_2$ (at 8.1 T) will also be briefly reviewed. Robert A. Welch Foundation grant No.F-1191 and the National Science Foundation grant No. DMR-0210383. [Preview Abstract] |
Thursday, March 16, 2006 12:03PM - 12:15PM |
V9.00005: Three-dimensional Imaging using Magnetic Resonance Force Microscopy I. H. Lee, K.C. Fong, Yu. Obukhov, D.V. Pelekhov , P.C. Hammel We describe techniques for obtaining 3D spin density images using Magnetic Resonance Force Microscopy. The apparatus, specifically designed to test imaging techniques, operates in vacuum at room temperature. We record the spatial dependence of the force generated by the Electron Spin Resonance signal from a DPPH particle mounted on the cantilever as it is scanned over a spherical NdFeB particle used as a high gradient probe magnet. Details of apparatus design, experimental data, challenges and approaches to 3D MRFM image deconvolution will be presented. [Preview Abstract] |
Thursday, March 16, 2006 12:15PM - 12:27PM |
V9.00006: Development of a Room Temperature High Sensitivity Magnetoelectric Scanning Microscope Jason Hattrick-Simpers, Liyang Dai, Ichiro Takeuchi, Manfred Wuttig In recent years the interest in magnetoelectric (ME) materials has increased dramatically, since they promise to have a number of unique functionalities and capabilities including ultrahigh magnetic field sensitivity. To date there has been little work done to actually use them in applications. We have constructed a high sensitivity room temperature scanning magnetic field microscope using a ME composite device made of a metglass/xyz(PVDF)/metglass sandwitch structured laminate. The smallest ME composite device used was 1 mm x 2 mm x 200 microns. The ME coefficient and the peak voltage of a typical device are 50 mV/Gcm and 3 mV at an AC modulation field of 10 Gauss. Scans of a conducting ring carrying an AC current, with the sensor DC biased at 100 Gauss, will be shown for various ring dimensions and AC currents. Through the variation of AC current we have shown that the sensitivity of the microscope to the z-axis component of AC field is better than 10$^{-9}$ T. We will discuss the relationship between the ME device dimensions and the spatial resolution of the microscope. [Preview Abstract] |
Thursday, March 16, 2006 12:27PM - 12:39PM |
V9.00007: Feature doubling in MFM imaging Zhifeng Deng, Erhan Yenilmez, Hongjie Dai, Kathryn Moler Recently, magnetic material coated nanotube tips have been used for high resolution magnetic force microscopy. It is convenient to control the total thickness of a metal-coated nanotube by change the nominal deposition thickness. The thinner the coating is, the less magnetic material attaches to the nanotube. With cobalt coated nanotube tip eleven nanometers in diameter, we measure twenty-five nanometer features clearly. We also observe feature doubling with cobalt coated carbon nanotube tips in an experimental hard drive sample, indicating paramagnetic behavior for the smallest tips. [Preview Abstract] |
Thursday, March 16, 2006 12:39PM - 12:51PM |
V9.00008: Progress of Magnetic Force Microscope for detecting spin-polarized electrons in non-magnetic materials V.P. Bhallamudi, Y. Jung, D.V. Pelekhov, Yu Obukhov, P.C. Hammel, T. Mewes While optical methods for detection of spin-polarized currents and spin accumulation in non-magnetic materials have proved quite successful, their applicability is limited to certain class of materials. Magnetic force microscopy (MFM) offers a more widely applicable alternative. We report here on the progress towards building such a high sensitivity low temperature-MFM spin detector. It employs optical interferometry for displacement detection. Issues related to techniques for detection and various challenges are discussed. Sample images demonstrating the high force sensitivity of the microscope are also presented. [Preview Abstract] |
Thursday, March 16, 2006 12:51PM - 1:03PM |
V9.00009: Focused ion beam deposition of Co$_{71}$Cr$_{17}$Pt$_{12}$ and Ni$_{80}$Fe$_{20}$ on tips for magnetic force microscopy Alfred Lee, Changbae Hyun, Alex de Lozanne We demonstrate that a focused ion beam can deposit magnetic coatings on cantilevers used for atomic force microscopy, thereby producing a sensor for magnetic force microscopy. This technique is highly versatile, allowing the convenient deposition of complex or expensive materials, such as Co$_{71}$Cr$_{17}$Pt$_{12}$. A second material chosen for this demonstration was permalloy (Ni$_{80}$Fe$_{20})$. We show magnetic images acquired with these cantilevers to illustrate their excellent properties and the differences between coatings. In principle, multilayer coatings could be easily made with this technique. [Preview Abstract] |
Thursday, March 16, 2006 1:03PM - 1:15PM |
V9.00010: High-resolution scanning hall probe microscopy Clifford Hicks, Lan Luan, J. Hendrik Bluhm, Kathryn Moler, Janice Guikema, Eli Zeldov, Hadas Shtrikman Scanning hall sensors can be used to directly image magnetic fields at surfaces. They offer high resolution, high sensitivity, operability over a broad temperature range, and linearity. We have fabricated hall sensors on GaAs / Al$_{0.35}$Ga$_{0.65}$As and GaAs / Al$_{0.3}$Ga$_{0.7}$As heterostructures containing 2D electron gases 40, 39 and 140nm beneath the surface. The sensitive areas of our probes range from microns to 85nm on a side. We report on the field sensitivities of probes of various sizes and their spatial resolution in a scanning configuration. [Preview Abstract] |
Thursday, March 16, 2006 1:15PM - 1:27PM |
V9.00011: Scanning Hall Probe Microscopy (SHPM) using Quartz Crystal AFM Feedback Munir Dede, Koray Urkmen, Ahmet Oral, Ian Farrer, David Ritchie Scanning Hall Probe Microscopy (SHPM)[1] is a quantitative and non-invasive technique for imaging localized surface magnetic field fluctuations such as ferromagnetic domains with high spatial and magnetic field resolution of $\sim $50nm {\&} 7mG/Hz$^{-1/2}$ at room temperature. In the SHPM technique, Scanning Tunneling Microscope(STM)[1] or Atomic Force Microscope(AFM)[2] feedback is usually used for bringing the Hall sensor into close proximity of the sample. In the latter, the Hall probe has to be integrated with an AFM cantilever in a complicated microfabrication process. In this work, we have eliminated the difficult cantilever-Hall probe integration process; a Hall sensor is simply glued at the end of 32,768Hz Quartz tuning fork, as force sensor. The sensor assembly is set to oscillate with a PLL. SHPM electronics is modified to detect AFM topography and the frequency shift, along with the magnetic field image. The resonant frequency of the sensor drops to $\sim $5 kHz due to mass of the Hall sensor. Hard Disk, NdFeB Magnet, Garnet samples are imaged with the Quartz Crystal AFM feedback and the performance is found to be comparable with the SHPM using STM feedback. Quartz Crystal AFM feedback offers a very simple sensor fabrication and operation in SHPM. This method eliminates the necessity of conducting samples for SHPM. [1] A. Oral \textit{et. al.} Appl. Phys. Lett., 69, 1324 (1996) [2] A.J. Brook \textit{et. al.} Appl. Phys. Lett. 82, 3538 (2003) [Preview Abstract] |
Thursday, March 16, 2006 1:27PM - 1:39PM |
V9.00012: Approach to Dipolar Field Microscopy Carlos Meriles, Wei Dong, Phillip Stallworth Nuclear Magnetic Resonance (NMR) is arguably one of the most powerful techniques available today to characterize diverse systems. However, the low sensitivity of the standard detection method constrains the applicability of this technique to samples having effective dimensions not less than a few microns. Here, we propose a novel scheme and device for the indirect detection of the nuclear spin signal at a submicroscopic scale. This approach -- for which the name Dipolar Field Microscopy (DFM) is suggested -- is based on the manipulation of the long-range nuclear dipolar interaction created between the sample and a semiconductor tip located close to its surface. After a preparation interval, the local magnetization of the sample is used to modulate the nuclear magnetization in the semiconductor tip, which, in turn is determined by an optical inspection. Based on results previously reported, it is shown that, in principle, images and/or localized high-resolution spectra of the sample can be retrieved with spatial resolution proportional to the size of the tip. These calculations are accompanied by recent proof-of-principle experimental results in a model system. [Preview Abstract] |
Thursday, March 16, 2006 1:39PM - 1:51PM |
V9.00013: Force-gradient detection of electron spin resonance Neil Jenkins, John Marohn Electron spin resonance of single unpaired electron spins in fused silica has recently been demonstrated [Rugar, \emph{et al}, \emph{Nature} \textbf{430} 329 (2004)]. The techniques employed rely on being able to coherently modulate electron spin magnetization for many hundreds of milliseconds, and are thus not well suited for observing unpaired electrons in spin-labeled biomolecules, for example, where the relevant spin relaxation times will be orders of magnitude shorter. In this presentation, we will discuss force gradient methods for detecting and imaging electron spin resonance that are more generally applicable. In our methods, applied rf is used to cyclically saturate electron spin magnetization at twice the cantilever frequency. A theory for the effect will be presented and data from sample-on-cantilever experiments performed at cryogenic temperatures will compare conventional force-detected MRFM to the signal from the force gradient experiment. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700