Antonio, Darío (2009) Magnetómetros de alta sensibilidad implementados con micro-osciladores mecánicos / High sensitivity magnetometers implemented with mechanical micro-oscillators. Tesis Doctoral en Física, Universidad Nacional de Cuyo, Instituto Balseiro.
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Resumen en español
En esta tesis describimos el diseño, la fabricación y distintas aplicaciones de micromagnetometros para la medición de propiedades magnéticas en muestras micro- y nano- métricas. Estos dispositivos están compuestos por un microoscilador mecánico de alto Q, sensible a las variaciones de campo y momento magnético, y por la electrónica que acondiciona y amplifica las señales que este produce. En el Capítulo 4 presentamos los distintos osciladores fabricados, sus características principales y los métodos utilizados para su excitación y detección. A continuación en el Capítulo 5 detallamos el proceso de diseño y fabricación del amplificador criogénico de transimpedancia integrado que utilizamos para la detección de las oscilaciones mecánicas. El alto Q del oscilador y la posibilidad de detectar cambios en su frecuencia de resonancia de aproximadamente 10mHz nos permiten alcanzar sensibilidades del orden de 10-¹⁸ Nm en torque, y del orden de 10-¹⁶Am"2 en momento magnético, cuando se aplica un campo magnético del orden de 10 kOe. Finalmente en el Capítulo 6 completamos la presentación de los osciladores con el desarrollo de un modelo analítico que describe correctamente su dinámica en los rangos de operación lineal y no-lineal. En cuanto a la implementación de los micromagnetometros, en el Capítulo 7 mostramos como se pueden aplicar a la detección de campos magnéticos externos, utilizándolos en el rango no-lineal y sin necesidad de incorporarle materiales magnéticos al oscilador. Luego en el Capítulo 8 presentamos mediciones de la respuesta magnética de dos nanotubos de manganita con campo magnético aplicado en la dirección perpendicular al eje fácil de magnetización. A partir de ellas obtenemos resultados cuantitativos para la magnetización de saturación, la constante de anisótropa y la susceptibilidad de campos bajos. Además observamos dos regímenes de magnetización diferentes en función de campo magnético, separados por una transición abrupta que esta acompañada por un pico de disipación. Finalmente, en el Capítulo 9 mostramos las mediciones de propiedades magnéticas realizadas en un lm de Nb superconductor de 20x20 μm"2 de superficie y con un espesor de 110 nm. En las curvas de momento magnético en función de campo aplicado y temperatura observamos discontinuidades o picos característicos del régimen mesoscópico. Este comportamiento es cualitativamente diferente al observado en muestras macroscópicas y esta asociado a eventos discretos de entrada de vórtices en el material. Su detección confirma a los micro magnetómetros como herramientas apropiadas para la medición de propiedades magnéticas en la micro- y nano- escala.
Resumen en inglés
The study of magnetism in micro- and nano- structures has attracted a lot of interest in both basic physics and technological applications research. This relevance is due to the dramatic modication of the physical properties as sizes are reduced below certain characteristic lengths and by a large array of applications such as ultra-high density magnetic recording, spin electronics, and magnetic force microscopy, among others. Manipulating and sensing these type of samples is a challenging task which often requires the development of new tools and technologies. In this thesis we present the design, fabrication and implementation of high sensitivity magnetometers based on micromechanical oscillators. These devices, fabricated with MEMS technology, extend all the advantages of high-Q mechanical oscillators to the microscopic scale oering the benets of reduced size, low cost, high sensitivity, direct integration with electronics, and low power. First, we describe the dierent fabricated designs, their main characteristics, and the methods used for their actuation and detection. Next, we describe the design and fabrication of the cryogenic electronics for the sensor, developed in order to investigate samples at low temperatures and with maximum sensitivity. The device consists of a transimpedance amplier that works at a broad range of temperatures, from room temperature down to 2K and was realized with a standard complementary metal oxide semiconductor 1.5 m process. Measurements of current-voltage characteristics, open-loop gain, input referred noise current, and power consumption are presented as a function of temperature. The integration of the high-Q oscillator with this cryogenic electronics results in a micromagnetometer that allows detection of magnetic moments as small as 10-¹³ emu. To complete the presentation of the micromagnetometer we describe our analytical model for the dynamics of an electrostatically actuated torsional oscillator, and its experimental validation. While at low excitations the system is well described by a damped linear oscillator, at higher oscillation amplitudes a non linear regime is observed. Nonlinearity is originated exclusively by the electrostatic driving and detection, and can be tuned by modifying the excitation or detection bias voltages. The parameters of the analytical model are obtained from the device dimensions and material properties. No empirical or tting parameters are needed except for the quality factor, which is extracted from the linear resonance curve. The proposed model can be a valuable and straightforward tool for the design and analysis of many other similar devices based on electrostatically actuated mechanical resonators. After this exhaustive presentation, the remaining of the thesis is dedicated to the description of three dierent implementations of the micromagnetometer. First, we use the device operating in its nonlinear regime to measure external magnetic eld. When the resonator is driven into resonance and a magnetic eld is applied, the induced currents originate damping in the mechanical system. If the resonator is nonlinear this damping produces signicant variations in the peak frequency that can be measured with good sensitivity due to its high Q. Thus, the sensor does not require incorporation of magnetic materials and is appropriate for fabrication with standard micromachining processes. Additionally we introduce an analytical model that correctly describes the device in the linear and nonlinear regimes. The model takes in account the electrostatic excitation and detection, and incorporates the operation dependence with the applied magnetic field. Second, we study both experimentally and theoretically the magnetic behavior of two isolated ferromagnetic nanotubes of perovskite La_0:67Ca_0:33MnO_3.We investigate the specic conguration where a magnetic field H is applied perpendicular to the magnetic easy axis of an isolated nanotube characterized by an uniaxial anisotropy constant K. In this situation, the magnetization M reduces the effective elastic constant of the resonator. This softening of the mechanical system is opposed to the hardening effect of M observed in a previous work, where H was applied parallel to the easy axis. Moreover, in this magnetic field conguration two distinct magnetization regimes are manifested, depending on the magnitude of H. For H»2K M the magnetization is almost parallel to the applied magnetic field and for H«2K M it is almost parallel to the easy axis of the nanotube. At a certain value of H there is a sharp transition from one regime to the other, accompanied by a peak in the energy dissipation. Finally, we measure the magnetic response of a 110nm lm of superconducting Nb with dimensions 20x20 μm"2. The magnetization vs. temperature and applied magnetic eld curves show discontinuities or peaks, related to the entrance of vortex in the sample. This behaviour is due to the interaction between the conned vortex inside the sample and the surface currents. The discontinuities are typical of the mesoscopic scale and disappear in macroscopic samples. The possibility of measuring these small signals conrm the micromagnetometers as suitable tools for the measurement of magnetic properties at the micro- and nanoscales.
| Tipo de objeto: | Tesis (Tesis Doctoral en Física) |
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| Palabras Clave: | Magnetic properties; Propiedades magnéticas; [Micromagnetometers; Micromagnetómetros; Oscillators; Osciladores] |
| Referencias: | [1] K. E. Johnson, \Thin-_lm recording media: Challenges for physics and magnetism in the 1990s," J. Appl. Phys., vol. 69, pp. 4932-4937, 1991. [2] Y. Martin and H. K. Wickramasinghe, \Magnetic imaging by \force microscopy" with 1000_A resolution," Appl. Phys. Lett., vol. 50, pp. 1455-1457, 1987. [3] S. A. Wolf, D. D. Awschalom, A. Buhrman, J. M. Daughton, S. von Moln_ar, M. L. Roukes, A. Y. Chtchelkanova, and D. M. Treger, \Spintronics: A spinbased electronics vision for the future," Science, vol. 294, pp. 1488-1495, 2001. [4] E. M. Chudnovsky and L. Gunther, \Quantum tunneling of magnetization in small ferromagnetic particles," Phys. Rev. Lett., vol. 60, pp. 661-664, 1988. [5] A. K. Geim, I. V. Grigorieva, S. V. Dubonos, J. G. S. Lok, J. C. Maan, A. Filippov, and F. Peeters, \Phase transitions in individual sub-micrometre superconductors," Nature, vol. 390, pp. 259{262, 1997. [6] N. C. Koshnick, H. Bluhm, M. E. Huber, and K. A. Moler, \Fluctuation superconductivity in mesoscopic aluminum rings," Science, vol. 318, pp. 1440-1443, 2007. [7] A. D. Hern_andez and D. Dom__nguez, \Surface barrier in mesoscopic type-I and type-II superconductors," Physical Review B, vol. 65, p. 144529, 2002. [8] ||, \The ac magnetic response of mesoscopic type II superconductors," Physical Review B, vol. 66, p. 144505, 2002. [9] D. Antonio, \Transiciones de fase y disipación en superconductores mesoscópicos," Tesis de Maestría en Física - Instituto Balseiro, 2004. [10] J. M. Elzerman, R. Hanson, L. H. W. van Beveren, B. Witkamp, L. M. K. Vandersypen, and L. P. Kouwenhoven, \Single-shot read-out of an individual electron spin in a quantum dot," Nature, vol. 430, p. 431, 2004. [11] V. Bouchiat, \Detection of magnetic moments using a nano-squid: limits of resolution and sensitivity in near-field squid magnetometry," Supercond. Sci. Technol., vol. 22, p. 064002, 2009. [12] D. Rugar, R. Budakian, H. J. Mamin, and B. W. Chui, \Single spin detection by magnetic resonance force microscopy," Nature, vol. 430, pp. 329-332, 2004. [13] A. K. Geim, S. V. Dubonos, J. G. S. Lok, I. V. Grigorieva, J. C. Maan, L. T. Hansen, and P. E. Lindelof, \Ballistic Hall micromagnetometry," Appl. Phys. Lett., vol. 71, pp. 2379{2381, 1997. [14] W. Wernsdotfer, K. Hasselbach, A. Benoit, B. Barbara, D. Mailly, J. Tuaillon, J. P. Perez, V. Dupuis, J. P. Dupin, G. Guiraud, and A. Perex, \High sensitivity magnetization measurements of nanoscale cobalt clusters," J. Appl. Phys., vol. 78, pp. 7192-7195, 1995. [15] M. E. Huber, N. C. Koshnick, H. Bluhm, L. J. Archuleta, T. Azua, P. G. Bjornsson, B. W. Gardner, S. T. Halloran, E. A. Lucero, and K. A. Moler,\Gradiometric micro-squid susceptometer for scanning measurements of mesoscopic samples," Rev. Of Sci. Instr., vol. 79, p. 053704, 2008. [16] J. Moreland, \Micromechanical instruments for ferromagnetic measurements," J. Phys. D: Appl. Phys., vol. 36, pp. R39-R51, 2003. [17] R. P. Cowburn, A. M. Moulin, and M. E. Welland, \High sensitivity measurement of magnetic _elds using microcantilevers," Appl. Phys. Lett., vol. 71, p. 2202, 1997. [18] C. A. Bolle, V. Aksyuk, F. Pardo, P. L. Gammel, E. Zeldov, E. Bucher, R. Boie, D. J. Bishop, and D. R. Nelson, \Observation of mesoscopic vortex physics using micromechanical oscillators," Nature, vol. 399, pp. 43-46, 1999. [19] MEMSCAP Inc., 4021 Stirrup Creek Drive, Durham, NC 27703, USA, http://www.memscap.com. [20] J. Carter, A. Cowen, B. Hardy, R. Mahadevan, M. Stone_eld, and S. Wilcenski, PolyMUMPs Design Handbook, Revision 11, MEMSCAP Inc. [21] G. Barillaro, A. Molfese, A. Nannini, and F. Pieri, \Analysis, simulation and relative performances of two kinds of serpentine springs," J. Micromech. Microeng., vol. 15, pp. 736-746, 2005. [22] W. N. Sharpe, Jr., K. Jackson, G. Coles, and D. A. LaVan, \Mechanical properties of di_erent polysilicons," ASME Symposium on Micro-Electro- Mechanical Systems (MEMS), vol. 2, pp. 255-259, November 5-10, 2000. [23] S. D. Senturia, Microsystem Design. Kluwer Academic Publishers, 2001. [24] N. Yazdi, H. Kulah, and K. Naja_, \Precision readout circuits for capacitive microaccelerometers," in Third IEEE International Conference on Sensors, Vienna, Austria, Oct. 2004, pp. 28{31. [25] B. E. Boser, \Electronics for micromachined inertial sensors," in Transducers '97, 1997 International Conference on Solid State Sensors and Actuators, Chicago, Jun. 1997, pp. 1169-1172. [26] G. K. Wong, \Torsional oscillators," in Experimental Techniques in Conden-sed Matter Physics at Low Temperatures, ser. Frontiers in Physics, R. C. Richardson and E. N. Smith, Eds. Addison-Wesley, 1988, ch. 4. [27] P. Horowitz and W. Hill, The Art of Electronics, 2nd ed. Cambridge University Press, Cambridge, 1989. [28] R. Kirschman, \Cold electronics: an overview," Cryogenics, vol. 25, pp. 115-122, 1985. [29] F. Balestra and G. Ghibaudo, Device and Circuit Cryogenic Operation for Low Temperature Electronics. Boston/Dordrecht/London: Kluwer Academic Publishers, 2001. [30] J. T. Hastings and K. W. Ng, \Characterization of a complementary metaloxide semiconductor operational ampli_er from 300 to 4.2 K," Rev. of Sci. Instr., vol. 66, pp. 3691{3696, 1995. [31] EECS Department of the University of California, \The spice page," http://bwrc.eecs.berkeley.edu/Classes/icbook/SPICE/. [32] D. Johns and K. Martin, Analog integrated circuit design. John Wiley & Sons, Inc., 1997. [33] S. K. Tewksbury, \N-channel enhancement-mode MOSFET characteristics from 10 to 300K," IEEE Trans. Electron Devices, vol. 28-12, pp. 1519-1529, 1981. [34] R. Wang, J. Dunkley, T. A. DeMassa, and L. F. Jelsma, \Threshold voltage variations with temperature in MOS transistors," IEEE Trans. Electron Devices, vol. 18-6, pp. 386-388, 1971. [35] B. Razavi, Design of Analog CMOS Integrated Circuits. Mc Graw Hill, New York, 2001. [36] H. Nagata, H. Shibai, T. Hirao, T. Watabe, M. Noda, Y. Hibi, M. Kawada, and T. Nakagawa, \Cryogenic capacitive transimpedance amplifler for astronomical infrared detectors," IEEE Trans. Electron Devices, vol. 51-2, pp. 270-278, 2004. [37] S. Liu, J. Kramer, G. Indiveri, T. Delbruck, and R. Douglas, Analog VLSI: Circuits and Principles. The MIT Press, 2002. [38] P. Allen and D. Holberg, CMOS Analog Circuit Design. Oxford: Oxford University Press, 1987. [39] S. Sesnic and G. Craig, \Thermal e_ects in JFET and MOSFET devices at cryogenic temperatures," IEEE Trans. Electron Devices, vol. 19-8, pp. 933-942, 1972. [40] J. F. Rhoads, S. W. Shaw, and K. L. Turner, \Nonlinear dynamics and its applications in micro- and nanoresonators," Birck and NCN Publications, vol. Proceedings of DSCC2008 2008 ASME Dynamic Systems and Control Conference, 2008, http://docs.lib.purdue.edu/nanopub/158. [41] R. P. Feynman, R. B. Leighton, and M. Sands, The Feynman Lectures on Physics, Vol. 1, 2nd ed. Addison - Wesley, 1964. [42] J. Guckenheimer and P. Holmes, Nonlinear oscillations, dynamical systems, and bifurcations of vector fields, 2nd ed., ser. Applied Mathematical Sciences. Springer-Verlag, 1986, vol. 42. [43] L. D. Landau and E. M. Lifshitz, Mechanics, 3rd ed., ser. Course of Theoretical Physics. Pergamon Press, 1976, vol. 1. [44] H. H. Yang, N. V. Myung, J. Yee, D. Y. Park, B. Y. Yoo, M. Schwartz, K. Nobe, and J. W. Judy, \Ferromagnetic micromechanical magnetometer," Sensors and Actuators A, vol. 97-98, pp. 88-97, 2002. [45] M. I. Dolz, W. Bast, D. Antonio, H. Pastoriza, J. Curiale, R. D. S_anchez, and A. G. Leyva, \Magnetic behavior of single La0:67Ca0:33MnO3 nanotubes: Surface and shape e_ects," J. Appl. Phys., vol. 103, p. 083909, 2008. [46] D. S. Greywall, \Sensitive magnetometer incorporating a high-Q nonlinear mechanical resonator," Meas. Sci. Technol., vol. 16, pp. 2473-2482, 2005. [47] B. Yurke, D. S. Greywall, A. N. Pargellis, and P. A. Busch, \Theory of ampli_er-noise evasion in an oscillator employing a nonlinear resonator," Phys. Rev. A, vol. 51, pp. 4211-4229, 1995. [48] J. D. Jackson, Classical Electrodynamics, 2nd ed. John Wiley & Sons, Inc., 1975. [49] A. F. Kip, Fundamentals of Electricity and Magnetism, 1st ed., ser. Fundamentals of Modern Physics. New York: Mc Graw-Hill, 1962. [50] D. S. Greywall, B. Yurke, P. A. Busch, A. N. Pargellis, and R. L. Willett,\Evading ampli_er noise in nonlinear oscillators," Phys. Rev. Lett., vol. 72, pp. 2992-2995, 1994. [51] H. W. C. Postma, T. Teepen, Z. Yao, M. Grifoni, and C. Dekker, \Carbon nanotube single-electron transistors at room temperature," Science, vol. 293, pp. 76-79, 2001. [52] A. Bachtold, P. Hadley, T. Nakanishi, and C. Dekker, \Logic circuits with carbon nanotube transistors," Science, vol. 294, pp. 1317-1320, 2001. [53] L. Hueso and N. Mathur, \Dreams of a hollow future," Nature, vol. 427, pp. 301-304, 2004. [54] E. Comini, G. Faglia, G. Sberveglieri, Z. Pan, and Z. L. Wang, \Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts," Appl. Phys. Lett., vol. 81, p. 1869, 2002. [55] A. G. Leyva, J. Curiale, H. Troiani, M. Rosenbusch, P. Levy, and R. D. Sanchez, \Nanoparticles of La(1x)SrxMnO3 (x = 0:33; 0:20) assembled into hollow nanostructures for solid oxide fuel cells," Adv. Sci. Technol., vol. 51, pp. 54-59, 2006. [56] B. D. Cullity, Introduction to Magnetic Materials. Addison-Wesley, 1972. [57] P. Levy, A. G. Leyva, H. Troiani, and R. D. S_anchez, \Nanotubes of rareearth manganese oxide," Appl. Phys. Lett., vol. 83, p. 5247, 2003. [58] P. Vargas and D. Laroze, \Thermodynamics of three-dimensional magnetic nanoparticles," J. Magn. Magn. Mater., vol. 272-276, pp. e1345-e1346, 2004. [59] M. I. Dolz, Medición de superconductores mesoscópicos mediante micro- electro-máquinas. Tesis Doctoral, Instituto Balseiro - UNC - CNEA, 2009. [60] J. J. Z_arate, \Ratchet de vórtices: experimentos en redes de junturas Josephson," Tesis de Maestría en Física - Instituto Balseiro, 2007. [61] B. W. Max_eld and W. L. McLean, \Superconducting penetration depth of Niobium," Physical Review, vol. 139, p. A1515, 1965. [62] B. D. Cullity, Introduction to Magnetic Materials. Addison-Wesley, 1972. [63] M. Tinkham, Introduction to Superconductivity. Kluwer Academic Publishers, 1996. [64] B. J. Baelus and F. M. Peeters, \Dependence of the vortex con_guration on the geometry of mesoscopic at samples," Phys. Rev. B, vol. 65, p. 104515, 2002. |
| Materias: | Física > Magnetismo |
| Divisiones: | Gcia. de área de Investigación y aplicaciones no nucleares > Gcia. de Física > Materia condensada > Bajas temperaturas |
| Código ID: | 1098 |
| Depositado Por: | Tamara Cárcamo |
| Depositado En: | 07 Sep 2022 15:24 |
| Última Modificación: | 07 Sep 2022 15:24 |
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