Background and activities
My research is focused on understanding the fundamental magnetic properties of rocks and minerals, and how the atomic-scale properties affect magnetic anomalies on local, regional and satellite scales. My projects and funding, have ranged from nanotechnology through mineral resource investigations to space-research programs. I received my PhD in 1993, and have over 80 publications in the international journals in the fields of rock and mineral magnetism, crustal magnetism, exploration, mineralogy, petrology and geochemistry. My research is highly interdisciplinary and my co-authors are in the fields of physics, chemistry, nanomaterials, crystallography and geophysics. In 2009, I gave the Bullard Lecture at the American Geophysical Union on the subject of Crustal Magnetism. I have given over 50 invited international lectures at international conferences and at universities around the world.
In 2012, I moved to NTNU from the Geological Survey of Norway, where I was a senior researcher. Since moving to NTNU I have built up a program focusing on the magnetic behaviour of crustal rocks at all scales (atomic to satellite) with 2 postdocs, 3PhDs, 4 masters students working on these topics.
I was a chair of the Advisory Board for the Institute of Rock Magnetism, University of Minnesota, USA. I am member of Det Kongelige Norske Videnskabers Selskab (The Royal Norwegian Society of Sciences and Letters), Norges Tekniske Vitenskapsakademi (Norwegian Academy of Technical Sciences), a Fellow of the Mineralogical Society of America and the Geological Society of America. Board member of the Deep research School (UiO) and National Geomagnetism Laboratory at UiO.
courses taught
TGB4285 Crustal Magnetism
TGB4280 Geophysical Exploration for Natural Resources
GB8110 Mineral and Crustal Magnetism
GB8105 Applied Geophysics and Petrology for Exploration of Natural Resources
Scientific, academic and artistic work
Displaying a selection of activities. See all publications in the database
2018
- (2018) Portrait of a giant deep-seated magmatic conduit system: The Seiland Igneous Province. Lithos. vol. 296-299.
- (2018) Magnetism at Depth: A View from an Ancient Continental Subduction and Collision Zone. Geochemistry Geophysics Geosystems.
2017
- (2017) Influence of static alternating field demagnetization on anisotropy of magnetic susceptibility: Experiments and implications. Geochemistry Geophysics Geosystems. vol. 18 (9).
- (2017) Effect of magnetic anisotropy on the natural remanent magnetization in the MCU IVe' layer of the Bjerkreim Sokndal Layered Intrusion, Rogaland, Southern Norway. Journal of Geophysical Research - Solid Earth. vol. 122 (2).
- (2017) Effects of magnetic anisotropy on total magnetic field anomalies. Journal of Geophysical Research - Solid Earth. vol. 122 (11).
- (2017) Spin orientation in solid solution hematite-ilmenite. American Mineralogist. vol. 102 (6).
- (2017) Examining origins of magnetic anomalies at the crystal scale using scanning magnetic microscopy. Exploration 17 . Decennial Mineral Exploration Conferences; Toronto. 2017-10-22 - 2017-10-26.
- (2017) Lamellar magnetism and exchange bias in billion-year-old metamorphic titanohematite with nanoscale ilmenite exsolution lamellae: II. Exchange-bias at 5 K after field-free cooling of NRM. Geophysical Journal International. vol. 208 (2).
2016
- (2016) Magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion, Rogaland, Southern Norway. Tectonophysics. vol. 688.
- (2016) Nonlinear Preisach maps: Detecting and characterizing separate remanent magnetic fractions in complex natural samples. Journal of Geophysical Research - Solid Earth. vol. 121 (12).
- (2016) Anatomy of a deep crustal volcanic conduit system; The Reinfjord Ultramafic Complex, Seiland Igneous Province, Northern Norway. Lithos. vol. 252-253.
- (2016) Crustal magnetic signature of planets: Tracking the solid solution of Fe and exsolution of magnetite in Bushveld plagioclase by magnetic and Mössbauer properties. Geological Society of America, Abstracts with Programs.
- (2016) Lamellar Magnetism and Exchange Bias in Billion-year-old Titanohematite with Nanoscale Ilmenite Exsolution Lamellae: I. Mineral and Magnetic Characterization. Geophysical Journal International. vol. 206 (1).
- (2016) The deep crustal structure of the mafic-ultramafic Seiland Igneous Province of Norway from 3D gravity modelling and geological implications. Geophysical Journal International. vol. 207 (3).
- (2016) Remanent magnetization, magnetic coupling and interface ionic configurations of intergrown rhombohedral and cubic Fe-Ti oxides: a short survey. American Mineralogist. vol. 101 (3).
- (2016) Palaeointensity, core thermal conductivity and the unknown age of the inner core. Geophysical Journal International. vol. 205 (2).
2015
- (2015) 916 Ma Pole for southwestern Baltica: Paleomagnetism of the Bjerkreim Sokndal Layered Intrusion, Rogaland Igneous Complex, southern Norway. Geophysical Journal International. vol. 203 (1).
- (2015) Magnetic mean-field modelling of solid solutions: Theoretical foundations and application to the hematite-ilmenite system. Geophysical Journal International.
2014
- (2014) Anisotropy of magnetic susceptibility versus lattice- and shape-preferred orientation in the Lac Tio hemo-ilmenite ore body (Grenville province, Quebec). Tectonophysics. vol. 629 (C).
- (2014) Experimental evidence for lamellar magnetism in hemo-ilmenite by polarized neutron scattering. Physical Review B. Condensed Matter and Materials Physics. vol. 89 (5).
- (2014) Ferroan Geikielite and Coupled Spinel-Rutile Exsolution from Titanohematite: Interface Characterization and Magnetic Properties. American Mineralogist. vol. 99 (8-9).
- (2014) Chemical and magnetic properties of rapidly cooled metastable ferri-ilmenite solid solutions - IV: The fine structure of self-reversed thermoremanent magnetization. Geophysical Journal International. vol. 196 (3).
2013
- (2013) Measuring the Curie temperature. Geochemistry Geophysics Geosystems. vol. 14 (4).
- (2013) Influence of lattice-preferred orientation with respect to magnetizing field on intensity of remanent magnetization in polycrystalline hemo-ilmenite. Geophysical Journal International. vol. 192 (2).
2012
- (2012) Paleomagnetism and magnetic mineralogy of Grenville metamorphic and igneous rocks, Adirondack Highlands, USA. Precambrian Research. vol. 212-213.
- (2012) Chemical and magnetic properties of rapidly cooled metastable ferri-ilmenite solid solutions: implications for magnetic self-reversal and exchange bias - III. Magnetic interactions in samples produced by Fe-Ti ordering. Geophysical Journal International. vol. 191 (3).
- (2012) Chemical and magnetic properties of rapidly cooled metastable ferri-ilmenite solid solutions: II. Chemical changes during quenching and annealing. Geophysical Journal International. vol. 188 (2).
- (2012) Size and shape dependence of the magnetic ordering temperature in nanoscale magnetic particles. Geophysical Journal International. vol. 191 (3).
2011
- (2011) Remanent Magnetism. Encyclopedia of Solid Earth Geophysics.
- (2011) Remanent Magnetism. Encyclopedia of Solid Earth Geophysics.
- (2011) Chemical and magnetic properties of rapidly cooled metastable ferri-ilmenite solid solutions: implications for magnetic self-reversal and exchange bias—I. Fe-Ti order transition in quenched synthetic ilmenite 61. Geophysical Journal International. vol. 186 (3).
2010
- (2010) Magnetic clusters in ilmenite-hematite solid solutions. Physical Review B. Condensed Matter and Materials Physics. vol. 81 (22).
- (2010) Spin orientation in a natural Ti-bearing hematite: Evidence for an out-of-plane component. American Mineralogist. vol. 95.
- (2010) Geometry of ionic arrangements and magnetic interactions in ordered ferri-ilmenite solid solutions and its effect on low-T magnetic behavior. Geochemistry Geophysics Geosystems. vol. 11 (5).
2009
- (2009) Magnetic field microscopy of rock samples using a giant magnetoresistance–based scanning magnetometer. Geochemistry Geophysics Geosystems. vol. 10 (10).
- (2009) The application of Lorentz transmission electron microscopy to the study of lamellar magnetism in hematite-ilmenite. American Mineralogist. vol. 94.
- (2009) High efficiency of natural lamellar remanent magnetisation in single grains of ilmeno-hematite calculated using Mössbauer spectroscopy. Earth and Planetary Science Letters. vol. 288.
- (2009) Remanent and induced magnetic anomalies over a layered intrusion: Effects from crystal fractionation and magma recharge. Tectonophysics. vol. 478.
- (2009) Crustal Magnetism, Lamellar Magnetism and Rocks That Remember. Elements. vol. 5.
- (2009) Mechanism of exchange bias for isolated nanoparticles embedded in an antiferromagnetic matrix. Physical Review B. Condensed Matter and Materials Physics. vol. 80.
2008
- (2008) Magnetic properties of anorthosites: A forgotten source for planetary magnetic anomalies?. Geophysical Research Letters. vol. 35 (2).
- (2008) A low-temperature phase diagram for ilmenite-rich compositions in the system Fe2O3-FeTiO3. American Mineralogist. vol. 93.
- (2008) Exchange bias identifies lamellar magnetism as the origin of the natural remanent magnetization in titanohematite with ilmenite exsolution from Modum, Norway. Earth and Planetary Science Letters. vol. 268.
- (2008) Magnetic petrology of the Devonian Achala Batholith, Argentina: titanohaematite as an indicator of highly oxidized magma during crystallization and cooling. Geophysical Journal International. vol. 175 (3).
2007
- (2007) Magnetic phases in hemo-ilmenite: Insight from low-velocity and high-field Mössbauer spectroscopy. Geophysical Research Letters. vol. 34.
- (2007) Low-temperature exchange coupling between Fe2O3 and FeTiO3: Insight into the mechanism of giant exchange bias in a natural nanoscale intergrowth. Physical Review B. Condensed Matter and Materials Physics. vol. 17.
- (2007) Magnetic exchange bias of more than 1 Tesla in a natural mineral intergrowth. Nature Nanotechnology. vol. 2.
- (2007) Magnetization of exsolution intergrowths of hematite and ilmenite: Mineral chemistry, phase relations, and magnetic properties of hemo-ilmenite ores with micron- to nanometer-scale lamellae from Allard Lake, Quebec. Journal of Geophysical Research - Solid Earth. vol. 112 (B10).
- (2007) Magnetic properties and potential field modeling of the Peculiar Knob metamorphosed iron formation, South Australia: An analog for the source of the intense Martian magnetic anomalies?. Journal of Geophysical Research - Solid Earth. vol. 112 (B3).
2006
- (2006) Fe2+/Fe3+ charge ordering in contact layers of lamellar magnetism: Bond valence arguments. American Mineralogist. vol. 91.
- (2006) Crystallographic–magnetic correlations in single-crystal haemo-ilmenite: new evidence for lamellar magnetism. Geophysical Journal International. vol. 165.
2004
- (2004) The relationship between exsolution and magnetic properties in hemo-ilmenite: Insights from Mössbauer spectroscopy with implications for planetary magnetic anomalies. Geophysical Research Letters. vol. 31.
- (2004) Magnetic domain structures and stray fields of individual elongated magnetite grains revealed by magnetic force microscopy (MFM). Physics of the Earth and Planetary Interiors. vol. 141 (2).
- (2004) Effects of nanoscale exsolution in hematite–ilmenite on the acquisition of stable natural remanent magnetization. Earth and Planetary Science Letters. vol. 224.
- (2004) Earth analog for Martian magnetic anomalies: remanence properties of hemo-ilmenite norites in the Bjerkreim-Sokndal intrusion, Rogaland, Norway. Journal of Applied Geophysics. vol. 56 (3).
- (2004) Palaeomagnetism of the Egersund–Ogna anorthosite, Rogaland, Norway, and the position of Fennoscandia in the Late Proterozoic. Geophysical Journal International. vol. 158.
- (2004) What is magnetic in the lower crust?. Earth and Planetary Science Letters. vol. 226.
- (2004) Magnetic anomalies, layered intrusions and Mars. Geophysical Research Letters. vol. 31.
- (2004) Nature and origin of lamellar magnetism in the hematite-ilmenite series. American Mineralogist. vol. 89.
2002
- (2002) Nanoscale haematite–ilmenite lamellae in massive ilmenite rock: an example of ‘lamellar magnetism’ with implications for planetary magnetic anomalies. Geophysical Journal International. vol. 151 (3).
- (2002) Lamellar magnetism in the haematite–ilmenite series as an explanation for strong remanent magnetization. Nature. vol. 418.
2001
- (2001) Effect of fine-scale microstructures in titanohematite on the acquisition and stability of natural remanent magnetization in granulite facies metamorphic rocks, southwest Sweden: Implications for crustal magnetism. Journal of Geophysical Research - Solid Earth. vol. 106 (B12).
- (2001) Aeromagnetic anomalies, magnetic petrology, and rock magnetism of hemo-ilmenite- and magnetite-rich cumulate rocks from the Sokndal Region, South Rogaland, Norway. American Mineralogist. vol. 86.
- (2001) Minor element chemistry of hemo-ilmenite and magnetite in cumulate rocks from the Sokndal Region, South Rogaland, Norway. American Mineralogist. vol. 86.
2000
- (2000) A closer look at remanence-dominated aeromagnetic anomalies- Rock magnetic properties and magnetic mineralogy of the Russell Belt microcline-sillimanite gneiss, northwest Adirondack Mountains, New York. Journal of Geophysical Research - Solid Earth. vol. 105 (B7).
- (2000) Palaeomagnetism, rock magnetism and geochemistry of Jurassic dykes and correlative redbeds, Massachusetts, USA. Geophysical Journal International. vol. 143 (1).
1996
- (1996) A Barremian-Aptian (Early Cretaceous) North American paleomagnetic reference pole. Journal of Geophysical Research - Solid Earth. vol. 101 (B7).
- (1996) North America during the Lower Cretaceous: new palaeomagnetic constraints from intrusions in New England. Geophysical Journal International. vol. 126 (2).