Project

Back to overview

Magnetic thermodynamics of non-stoichiometric Fe-based mineral phases

English title Magnetic thermodynamics of non-stoichiometric Fe-based mineral phases
Applicant Gehring Andreas
Number 153173
Funding scheme Project funding
Research institution Institut für Geophysik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Mineralogy
Start/End 01.04.2014 - 31.03.2018
Approved amount 236'596.00
Show all

All Disciplines (2)

Discipline
Mineralogy
Material Sciences

Keywords (11)

magnetic thermodynamics; solid solutions; mixed-valent oxide; lattice defects; ac/dc magnetometry; magnetic materials; small-angle neutron scattering; electron spin resonance; rock magnetism; monosulfide; cation doping

Lay Summary (German)

Lead
Nicht-stöchiometrische Minerale sind wichtige Indikatoren für chemische und physikalische Prozesse und ermöglichen einen vertieften Einblick in die Entstehungsgeschichte der Erdkruste und extra-terrestrischen Gesteinen. Von beonderer Bedeutung sind die Festlösungen von Eisen- und Titan-Oxiden (Hämatit-Ilmenit-Magnetit) und Monosulfiden (Fe1-x S; 0 < x = 0.125), die wichtige Remanenzträgern in Gesteinen sind. Es hat sich gezeigt, dass die Abweichung von der Stöchiometrie das magnetische Verhalten von Oxiden und Sulfiden starkt beeinflusst. Diese Mineralphasen werden in der Paleomagnetik weit verbreitet angewendet um tektonische Prozesse auf der Erde zu rekonstruieren und ihr Auftreten in Meteoriten erlauben Rückschlüsse auf die Magnetisierung anderer Planeten (z.B. Mars) zu ziehen. Obwohl diese magnetischen Minerale schon intensiv untersucht wurden, sind verschiedene Einflüsse der mineralogisch-chemischen Struktur auf die magnetische Eigenschaften noch nicht im Detail erforscht.
Lay summary

In unserem Projekt erforschen wir die Thermodynamik von Niobium substituierten Ilmenite und Hämoilmeniten sowie von monoklinenen Monosulfid Fe7S8. Zuerst werden natürliche Proben aus unterschiedlichen Orogenen untersucht mit dem Ziel (I) Einfluss der chemisch-strukturellen Variablilität auf die Magnetisierung von nicht-stöchiometrischen, eisenreichen Mineralien in einem physikalisches Modell zu beschreiben und (II) soll ein solches Modell verwendet werden, um die Remagnetisierung während tektonischer Prozesse in Gebirgszügen (z.B. Alpen) zu rekonstruieren. Die Ergebnisse der natürlichen Proben sind eine Grundlage für die Herstellung von synthetischen Proben, in welchen magnetische Effekte, die durch die Abweichung von der Stoichiometrie entstehen können, manipuliert werden kann. Solche geo-inspirierte Materialien bilden einen Beitrag zum vertieften Verständnis des Magnetismus in natürlichen Systemen und können zudem eine Möglichkeit bieten für die Entwicklung von Materialien mit einer technischen Anwendung.

Unsere Arbeit ist primär Grundlagenforschung in einem multidisziplinären Rahmen, der Erdwissenschaften, Materialwissenschaften und angewandte Physik einschliesst. Die Ergebnisse werden einen Beitrag leisten im Gebiet der Erdmaterialien, in welchem Prozesse der Natur abgeschaut werden und dann versucht wird sie auf einen Labormassstab zu übertragen.

Direct link to Lay Summary Last update: 16.04.2014

Responsible applicant and co-applicants

Employees

Publications

Publication
Ordered defects in Fe1-xS generate additional magnetic anisotropy symmetries
Koulialias Dimitrios, Charilaou Michalis, Schäublin Robin, Mensing Christian, Weidler Peter, Löffler Jörg, Gehring Andreas (2018), Ordered defects in Fe1-xS generate additional magnetic anisotropy symmetries, in Journal of Applied Physics, 123, 033902.
Torque analysis of incoherent spin rotation in the presence of ordered defects
Koulialias Dimitrios, Charilaou Michalis, Mensing Christian, Löffler Jörg, Gehring Andreas (2018), Torque analysis of incoherent spin rotation in the presence of ordered defects, in Applied Physics Letters, 112, 202404.
Variable defect structures cause the magnetic low-temperature transition in natural monoclinic pyrrhotite
Koulialias Dimitrios, Kind Jessica, Charilaou Michalis, Weidler Peter, Löffler Jörg, Gehring Andreas (2016), Variable defect structures cause the magnetic low-temperature transition in natural monoclinic pyrrhotite, in Geophysical Journal International, 204, 961-967.
Magneto-electronic coupling in modulated defect-structures of natural Fe1-xS
Charilaou Michalis, Kind jessica, Koulialias Dimitrios, Weidler Peter, Mensing Christian, Löffler Jörg, Gehring Andreas (2015), Magneto-electronic coupling in modulated defect-structures of natural Fe1-xS, in Journal of Applied Physics, 118(083903), 1-4.

Collaboration

Group / person Country
Types of collaboration
Prof. Jeschke Group ETH Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Prof. Hellman Group, Physics Department UC Berkeley United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Wöll Group Institut für Funktionelle Grenzflächen, KIT, Karlsruhe Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Laboratory of Natural Magnetism ETH Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
Prof. Dunin-Borkowski Group Forschungszentrum Jülich Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Laboratory of Inorganic Chemistry ETH Zurich Switzerland (Europe)
- Publication
- Research Infrastructure
Laboratory for Neutron Scattering at PSI Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
American Geophysical Union Fall meeting Talk given at a conference What causes the Besnus transition in monoclinic pyrrhotite? 12.12.2016 San Francisco, United States of America Gehring Andreas;
American Geophysical Union Fall Meeting Poster Low-temperature anisotropy changes in monoclinic pyrrhotite 12.12.2016 San Francisco, United States of America Koulialias Dimitrios;
Deutsche Physikalische Gesellschaft Talk given at a conference Magneto-electronic coupling in modulated defect-structures of natural Fe1-xS 06.03.2016 Regensburg, Germany Koulialias Dimitrios;
American Geophysical Union Fall Meeting Poster Ferromagnetic resonance of nanocrystal chains with competitive and cooperative anisotropy 14.12.2015 San Francisco, United States of America Koulialias Dimitrios;


Associated projects

Number Title Start Funding scheme
134806 Intrinsic decomposing tendency of hematite-ilmenite phases and its effect on static and dynamic magnetic properties 01.04.2011 Project funding
121844 Intrinsic decomposing tendency of hematite-ilmenite phases and its effect on static and dynamic magnetic properties 01.02.2009 Project funding

Abstract

The proposed project is the continuation of our research on the physical properties of Fe-based mineral phases, which are widespread in geological systems and can be readily synthesized in the laboratory. These minerals are of considerable interest because they are the major magnetic carriers in the Earth’s crust and their physical properties make them suitable as starting point to design functional materials. Fe-based minerals are often non-stoichiometric due to cation substitution and/or defect structures. The departure from non-stoichiometry can result in intrinsic effects on the magnetic thermodynamics and the physics behind them is the main purpose of this multidisciplinary project.The link between structure, non-stoichiometry, and magnetic thermodynamics is investigated using natural and synthetic 4C pyrrhotite (Fe7S8), a monosulfide with a defined defect structure, and ilmenite (FeTiO3) with Nb(IV) substitution for Ti(IV). The synthetic samples will be produced in powder form using the sealed silica technique or in single crystals performing the Czochralsky method. For the investigation the chemical and structural properties a combination of state-of-the art analytical tools is used such as X-ray diffraction, inductively coupled plasma-mass spectroscopy, and electron microscopy coupled to an energy-dispersive X-ray spectrometer. To describe the magnetic thermodynamics, i.e., the ordering scheme, a combination of static and dynamic measurement methods including ac/dc magnetometry and neutron scattering experiments will be applied in a low (2 -300 K) and a high (300 - 1000K) temperature range. Special attention will be given to generate a sound physical model to explain the low-temperature transition in 4C pyrrhotite at about 30 K and that will close a gap in our knowledge of the magnetic properties of non-stoichiometric monosulfides. The experimental work will be completed by electron magnetic resonance spectroscopy to analyze magnetic bulk properties of ilmentite and pyrrhotite, and, in particular, to get specific information about the chemical configuration of the paramagnetic Nb(IV) cations in the ilmentite structure. In addition to the strong experimental aspect of the proposal, numerical studies will be performed using Monte Carlo simulation and mean-field modeling in order to obtain a more quantitative understanding of the magnetic structure and magnetic order of these non-stoichiometic materials.The structural and magnetic properties of synthetic samples will be compared with those of natural samples from locations where their formation can be inferred from the geological settings (e.g., pyrrhotite from the Swiss Alps, ilmenite from the Ilmen Mountains in Russia). The different conditions of the natural and synthetic samples during their formation will be considered in order to constrain effects of geologically relevant parameters (e.g., pressure, cooling rate, element partitioning) on the structure, stoichiometry as well as magnetic thermodynamics. This information contributes to the understanding of chemical and physical processes in the Earth’s crust and on other planets.Apart from the relevance for the Earth science, the proposed experimental and numerical approach to study non-stoichiometry will strengthen the fundamental knowledge of magnetic mineral phases, and this in turn bridges to materials science, where structure-property relationships are key to develop new functional materials. The insight into the physics of non-stoichiometric monosulfides and mixed-valence oxides gained in the course of this project will therefore also be considered in terms of the design of functional magnetic materials for technical applications.
-