David J. Dunlop, FRSCProfessor(Geophysics) Geomagnetisim and Tectonics: Fundamental magnetic properties and domain structures of ferromagnetic oxides; chemical overprinting of magnetization in the laboratory and in nature; ocean floor and ophiolite magnetism; seafloor spreading; paleomagnetism of orogenic belts; thermal uplift histories. Telephone: (905)828-3968 e-mail: dunlop@physicsdomain Research | Papers | Post-Docs | Students |
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Brief CVB.A.Sc., Toronto (1963); M.A., Toronto, (1964); Ph.D., Toronto (1968). Postdoctoral, University of Tokyo (1968-69), Université de Paris (1969-70); Visiting Scientist, Lunar Science Institute and Johnson Space Center, Houston (1972); Canada-France Exchange Scientist, Université de Paris (1977-8) ; Visiting Professor of Canadian Studies, Leeds University (1983); Killam Research Fellow (1983-85); Visiting Scientist, USSR Academy of Sciences (1980, 1982, 1988); President, Canadian Geophysical Union (1985-87); Fellow of the American Geophysical Union (1987); Senior Research Fellow, Tokyo Institute of Technology (1989); Visiting Professor, Universität München (1990); Fellow of the Royal Society of Canada (1990); Visiting Scientist, CSIRO, Sydney, Australia (1992); Professeur Associé, Université de Montpellier (1997);Senior Research Fellow, Kyoto University (1997, 2003); Professeur Associe, Universite de Paris (2004); Louis Neel Medal, European Geophysical Society (1999); J. Tuzo Wilson Medal, Canadian Geophysical Union (1999); 175th Anniversary Banner honoree, University of Toronto (2002-3); Bancroft Award, Royal Society of Canada (2006); CAP Medal for Achievement in Physics, Canadian Association of Physicists (2007).Research InterestsPermanent or remanent magnetization of ferromagnetic oxides in rocks provides the only vector record of events in the early history of the Earth. Precisely similar remanences are used in magnetic memories of computers and in audio and video recording. Our research spans time scales from the laboratory to the age of the Earth. Its applications range from unravelling collision histories of tectonic plates to nanostructures used in magnetic recording. In fundamental magnetism, we are using powerful parallel-processor computers to calculate 2- and 3-dimensional micromagnetic states of ferromagnetic coupled-spin lattices. Local energy minimum states of up to 223 coupled spins have been found, as well as internal structures of hybrid Bloch-Neél domain walls. We are now tackling the difficult problem of transition paths and probabilities, using Monte Carlo and simulated annealing techniques. Experimentally we are well equipped with microscopes for observing magnetic domains and with magnetometers using SQUID and vibrating cantilever detectors for measuring the responses of domains to changing magnetic fields. In pursuit of the pseudo-single-domain problem in magnetite - the behaviour of several domains collectively as though they were only a single domain - we have produced crystals spanning the size range 30 nm to 150 µm. These have already yielded a wealth of exciting data. For example, large crystals after zero-field cooling to 77 K mimic single domains, behaving like crystals orders of magnitude smaller. In applications to paleomagnetism, we have recently demonstrated that it is possible to determine the magnitude of the ancient geomagnetic field as well as its direction using multidomain crystals. This is straightforward for single domains but not for multidomains, where all the classical Thellier laws are violated. Our work is also relevant to environmental magnetism. Our techniques for determining grain size and oxidation state using the Verwey transition in magnetite are widely used in global paleoclimate studies based on soil and loess profiles and oceanic sediment cores. Recent Publications"A more ancient shield", D. J. Dunlop, Nature (News & Views) 446, 623-625 (2007). "Three-dimensional micromagnetic modeling of randomly oriented magnetite grains (0.03-0.3 μm)", K. Fukuma & D. J. Dunlop, J. Geophys. Res. 111, B12S11, doi:10.1029/ 2006JB004562 (2006). "Magnetic memory and coupling between spin-canted and defect magnetism in hematite", O. Ozdemir & D. J. Dunlop, J. Geophys. Res. 111, B12S03, doi:10.1029/ 2006JB004555 (2006). "Day plots of mixtures of superparamagnetic, single-domain, pseudo-single-domain and multidomain magnetites", D. J. Dunlop & B. Carter-Stiglitz, J. Geophys. Res. 111, B12S09, doi:10.1029/ 2006JB004499 (2006). "Angular variation of the magnetic properties and reversal mode of aligned single-domain iron nanoparticles", G. A. Milne & D. J. Dunlop, J. Geophys. Res. 111, B12S08, doi:10.1029/ 2006JB004530 (2006). "Inverse thermoremanent magnetization", D. J. Dunlop, J. Geophys. Res. 111, B12S02, doi:10.1029/ 2006JB004572 (2006). "Testing the independence of partial TRMs of single-domain and multidomain grains: Implications for paleointensity determination", Y. J. Yu & D. J. Dunlop, J. Geophys. Res. 111, B12S31, doi:10.1029/ 2006JB004434 (2006). "Magnetic domain observations on magnetite crystals in biotite and hornblende crystals", O. Ozdemir & D. J. Dunlop, J. Geophys. Res. 111, B06103. doi:10.1029/ 2005JB004090 (2006). “Testing the independence law of partial ARMs: Implications for paleointensity determination, Y. J. Yu, D. J. Dunlop & Ö. Özdemir, Earth Planet. Sci. Lett. 208, 27-39 (2003). “Are ARM and TRM analogs? Thellier analysis of ARM and pseudo-Thellier analysis of TRM”, Y. J. Yu, D. J. Dunlop & Ö. Özdemir, Earth Planet. Sci. Lett. 205, 325-336 (2003). [PDF] “Low-temperature cycling of isothermal and anhysteretic remanence: microcoercivity and magnetic memory”, A. R. Muxworthy, D. J. Dunlop & Ö. Özdemir, Earth Planet. Sci. Lett. 205, 173-184 (2003). [PDF] “Multivectorial paleointensity determination from the Cordova Gabbro, southern Ontario”, Y. J. Yu & D. J. Dunlop, Earth Planet. Sci. Lett. 203, 983-998 (2002). [PDF] “Partial anhysteretic remanent magnetization in magnetite, 1. Additivity”, Y. J. Yu, D. J. Dunlop & Ö. Özdemir, J. Geophys. Res. 107 (B10), 2244, EPM 7-1 to 7-9. doi: 10.1029/ 2001JB001249 (2002). [PDF] “Partial anhysteretic remanent magnetization in magnetite, 2. Reciprocity”, Y. J. Yu, D. J. Dunlop & Ö. Özdemir, J. Geophys. Res. 107 (B10), 2245, EPM 8-1 to 8-9. doi: 10.1029/ 2001JB001269 (2002). [PDF] “First-order reversal curve (FORC) diagrams for pseudo-single-domain magnetites at high temperatures”, A. R. Muxworthy & D. J. Dunlop, Earth Planet. Sci. Lett. 203, 369-382 (2002). [PDF] “Thermoremanence and stable memory of single-domain hematites”, Ö. Özdemir & D. J. Dunlop, Geophys. Res. Lett. 29 (18), 1877, 24-1 to 24-4. doi: 10.1029/ 2002GL015597 (2002). [PDF] “Theory and application of the Day plot (Mrs/Ms vs. Hcr/Hc) 1. Theoretical curves and tests using titanomagnetite data”, D. J. Dunlop, J. Geophys. Res. 107 (B3), EPM 4-1 to 4-22. doi: 10.1029/ 2001JB000486 (2002). [PDF] “Theory and application of the Day plot (Mrs/Ms vs. Hcr/Hc) 2. Application to data for rocks, sediments and soils” D. J. Dunlop, J. Geophys. Res. 107 (B3), EPM 5-1 to 5-15. doi: 10.1029/ 2001JB000487 (2002). [PDF] “Changes in remanence, coercivity and domain state at low temperatures in magnetite”, Ö. Özdemir, D. J. Dunlop & B. M. Moskowitz, Earth Planet. Sci. Lett. 194, 343-358 (2002). [PDF] “Paleointensity determination on the late Precambrian Tudor Gabbro, Ontario” Y. J. Yu & D. J. Dunlop, J. Geophys. Res. 106, 26,331-26,343 (2001). [PDF] “Magnetic
properties of Kurokami pumices from Mt. Sakurajima,
“Beyond Néel=s theories: Thermal demagnetization of narrow-band partial thermoremanent magnetizations”, D. J. Dunlop & Ö. Özdemir, Phys. Earth Planet. Inter. 126, 43-57 (2001). [PDF] “Multidomain hematite: A source of planetary magnetic anomalies?” D. J. Dunlop & G. Kletetschka, Geophys. Res. Lett. 28, 3345-3348 (2001). [PDF] “Archeomagnetism of potsherds from Grand Banks, Ontario: A test of low paleointensities in Ontario around A.D. 1000”, C. Carvallo & D. J. Dunlop, Earth Planet. Sci. Lett. 186, 437-450 (2001). [PDF] Rock Magnetism: Fundamentals and Frontiers, 573 pp, D. J. Dunlop & Ö. Özdemir, Cambridge University Press, Cambridge and New York (paperback edition; publication date: April 2001). “Archeomagnetism of Ontario potsherds from the last 2000 years”, Y .J. Yu, D. J. Dunlop, L. Pavlish & M. Cooper, J. Geophys. Res. 105, 19,419-19,433 (2000). [PDF] “Intermediate magnetite formation during dehydration of goethite”, Ö. Özdemir & D. J. Dunlop, Earth Planet. Sci. Lett. 177, 59-67 (2000). [PDF] “Effect of grain size and domain state on thermal demagnetization tails”, D. J. Dunlop & Ö. Özdemir, Geophys. Res. Lett. 27, 1311-1314 (2000). [PDF] “Time-temperature relations for the remagnetization of pyrrhotite (Fe7S8) and their use in estimating paleotemperatures”, D. J. Dunlop, Ö. Özdemir, D. A. Clark & P. W. Schmidt, Earth Planet. Sci. Lett. 176, 107-116 (2000). [PDF] “Low-temperature properties of a single crystal of magnetite oriented along principal magnetic axes”, Ö. Özdemir & D. J. Dunlop, Earth Planet. Sci. Lett. 165, 229-239 (1999). [PDF] “Grain size dependence of two-dimensional micromagnetic structures for pseudo-single-domain magnetite (0.2!2.5 μm)”, K. Fukuma & D. J. Dunlop, Geophys. J. Int. 134, 843-848 (1998). “Thermoremanent magnetization of non-uniformly magnetized grains” (invited review paper), D. J. Dunlop, J. Geophys. Res. 103, 30561-30574 (1998). [PDF] “A regional paleomagnetic study of lithotectonic domains in the Central Gneiss Belt, Grenville Province, Ontario”, V. Costanzo Alvarez & D. J. Dunlop, Earth Planet. Sci. Lett. 157, 89-103 (1998). [PDF] “Single-domain-like behavior in a 3-mm natural single crystal of magnetite”, Ö. Özdemir & D. J. Dunlop, J. Geophys. Res. 103, 2549-2562 (1998). [PDF] “Paleomagnetism and paleothermometry of the Sydney Basin, 1. Thermoviscous and chemical overprinting of the Milton monzonite”, D. J. Dunlop, P. W. Schmidt, Ö. Özdemir & D. A. Clark, J. Geophys. Res. 102, 27271-27283 (1997). [PDF] “Paleomagnetism and paleothermometry of the Sydney Basin, 2. Origin of anomalously high unblocking temperatures”, D. J. Dunlop, Ö. Özdemir & P. W. Schmidt, J. Geophys. Res. 102, 27285-27295 (1997). [PDF] “Effect of crystal defects and internal stress on the domain structure and magnetic properties of magnetite”, Ö. Özdemir & D. J. Dunlop, J. Geophys. Res. 102, 20211-20224 (1997). [PDF] “Thermoremanence, anhysteretic remanence and susceptibility of submicron magnetites: Non-linear field dependence and variation with grain size”, D. J. Dunlop & K. S. Argyle, J. Geophys. Res. 102, 20199-20210 (1997). [PDF] “An improved algorithm for micromagnetics”, T. M. Wright, W. Williams & D. J. Dunlop, J. Geophys. Res. 102, 12085-12094 (1997). [PDF] Rock Magnetism: Fundamentals and Frontiers, 573 pp, D. J. Dunlop & Ö. Özdemir, Cambridge University Press, Cambridge and New York (publication date: July 1997). “Monte Carlo simulation of two-dimensional domain structures in magnetite”, K. Fukuma & D. J. Dunlop, J. Geophys. Res. 102, 5135-5143 (1997). [PDF] “Rock magnetic properties of iron ores and host rocks from the Peña Colorada mining district, western Mexico”, L. Alva-Valdivia, D. J. Dunlop & J. Urrutia-Fucugauchi, J. Appl. Geophys. 36, 105-122 (1996). “Micromagnetic modelling of Bloch walls with Néel caps in magnetite”, S. Xu & D.J. Dunlop, Geophys. Res. Lett., 23, 2819-2822 (1996). [PDF] “Thermoremanence and Néel temperature of goethite”, Ö. Özdemir & D. J. Dunlop, Geophys. Res. Lett. 23, 921-924 (1996). [PDF] “Toward a better understanding of the Lowrie-Fuller test”, S. Xu & D. J. Dunlop, J. Geophys. Res. 100, 22533-22542 (1995). [PDF] “Simulation of magnetic hysteresis in pseudo-single-domain grains of magnetite”, W. Williams & D. J. Dunlop, J. Geophys. Res. 100, 3859-3871 (1995). [PDF] “Closure domains in magnetite”, Ö. Özdemir, S. Xu & D. J. Dunlop, J. Geophys. Res. 100, 2193-2209 (1995). [PDF] “Magnetism in rocks” (invited American Geophysical Union 75th anniversary paper), D. J. Dunlop, J. Geophys. Res. 100, 2161-2174 (1995). [PDF] “Synopsis
of paleomagnetic studies in the Kapuskasing Structural Zone”, D. T. Symons, M. T. Lewchuk, D. J. Dunlop & 5 others,
“Transdomain thermoremanent magnetization”, D. J. Dunlop, A. J. Newell & R. J. Enkin, J. Geophys. Res. 99, 19741-19755 (1994). [PDF] “Micromagnetic modeling of two-dimensional domain structures in magnetite”, S. Xu, D. J. Dunlop & A. J. Newell, J. Geophys. Res. 99, 9035-9044 (1994). [PDF] “Theory of partial thermoremanent magnetization in multidomain grains: I. Repeated identical barriers to wall motion (single microcoercivity)”, D. J. Dunlop & S. Xu, J. Geophys. Res. 99, 9005-9023 (1994). [PDF] “Theory of partial thermoremanent magnetization in multidomain grains: II. Effect of microcoercivity distribution and comparison with experiment”, S. Xu & D. J. Dunlop, J. Geophys. Res. 99, 9025-9033 (1994). [PDF] “Paleomagnetism of the Red Lake greenstone belt, northwestern Ontario: Possible evidence for the timing of gold mineralization”, V. Costanzo-Alvarez & D. J. Dunlop, Earth Planet. Sci. Lett. 119, 599-615 (1993). “Thermal demagnetization of VRM and pTRM of single-domain magnetite: no evidence for anomalously high unblocking temperatures”, D. J. Dunlop & Ö. Özdemir, Geophys. Res. Lett. 20, 1939-1942 (1993). “Tectonothermal history in the Mattawa area, Ontario,
“Magnetic domain structures on a natural single crystal of magnetite”, Ö. Özdemir & D. J. Dunlop, Geophys. Res. Lett. 20, 1835-1838 (1993). “The effect of oxidation on the Verwey transition in magnetite”, Ö. Özdemir, D. J. Dunlop & B. M. Moskowitz, Geophys. Res. Lett. 20, 1671-1674 (1993). “A two-dimensional micromagnetic model of magnetizations and fields in magnetite”, A. J. Newell, D. J. Dunlop & W. Williams, J. Geophys. Res. 98, 9533-9549 (1993). “A generalization of the demagnetizing tensor for non-uniform magnetization”, A. J. Newell, W. Williams & D. J. Dunlop, J. Geophys. Res. 98, 9551-9555 (1993). “Effect of anisotropy on the paleomagnetic contact test for a Grenville dike”, H. Hyodo & D. J. Dunlop, J. Geophys. Res. 98, 7997-8017 (1993). “Chemical remanent magnetization during γFeOOH phase transformations”, Ö. Özdemir & D. J. Dunlop, J. Geophys. Res. 98, 4191-4198 (1993). “Theory of alternating field demagnetization of multidomain grains and implications for the origin of pseudo-single-domain remanence”, S. Xu & D. J. Dunlop, J. Geophys. Res. 98, 4183-4190 (1993). “Paleomagnetism of alkaline complexes and remagnetization in the Kapuskasing Structural Zone, Ontario, Canada”, V. Costanzo-Alvarez, D. J. Dunlop & L. J. Pesonen, J. Geophys. Res. 98, 4063-4079 (1993). PostdocsGraduate StudentsFormer graduate student: Dr. Claire Carvallo (Ph.D. 2004; now Maitre de Conferences at Institut de Mineralogie et Physique de la Matiere Condensee, Universite de Paris VI, France) Former graduate student: Dr. Yongjae Yu (Ph.D. 2002; now Assistant Professor, Department of Earth & Environmental Science, Chungnam University, Daejeon, South Korea) Former graduate student: Jeremy Brett (M.Sc. 1995; now runs his own geophysical consulting firm in Toronto) Former graduate student: Dr. Glenn Milne (M.Sc. 1993; now Associate Professor at Department of Geosciences, University of Durham, UK) Former graduate student: Dr. Andrew Newell (M.Sc. 1990; now Research Scientist in Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA) Former graduate student: Dr. Vincenzo Costanzo-Alvarez (M.Sc. 1986, Ph.D. 1990; now Professor and Chair, Department of Ciencas de la Terra, University Simon Bolivar, Caracas, Venezuela) Former graduate student: Dr. Hironobu Hyodo (M.Sc. 1984, Ph.D. 1989; now Professor at Research Institute of Natural Sciences, Okayama University of Science, Okayama, Japan) Former graduate student: Dr. Franz Heider (M.Sc. 1984, Ph.D. 1988; now Senior Research & Development Scientist at Infineon (Europe's largest semiconductor company), Villach, Austria) Former graduate student: Dr. Randolph Enkin (M.Sc. 1986; now Research Scientist, Pacific Geoscience Centre, Geological Survey of Canada, Sidney, BC) Former graduate student: Dr. Christopher Hale (Ph.D. 1985; now independent geophysical consultant, Hamilton, ON) Former graduate student: Kenneth Argyle (M.Sc. 1984; now partner in a firm of physical/ geophysical consultants) Former graduate student: Dr. Monika Bailey (M.Sc. 1975, Ph.D. 1980; now Research Scientist, Atmospheric Environment Service, Toronto, ON) Former graduate student: Dr. Kenneth Buchan (M.Sc. 1973, Ph.D. 1977; now Research Scientist, Geological Survey of Canada, Ottawa, ON) Former graduate student: Dr. Michael McWilliams (M.Sc. 1974; now Director, Division of Exploration Geoscience, CSIRO, Perth, Australia)
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