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Part III Options: Mineralogy

MA: Magnetoelastic Coupling in Minerals and Functional Materials

Michael Carpenter

6 lectures and 4 practicals

Magnetic and elastic properties are the two most important physical properties of minerals in a geological context because they have been used both to reconstruct the history of the Earth’s surface layers and to understand the structure and composition of the Earth with depth through to the inner core. It is not generally appreciated that the same properties can be strongly interdependent in minerals which undergo magnetic phase transitions. Furthermore, in an entirely different context, magnetoelastic coupling effects are pervasive in controlling the functional properties of materials such as multiferroics and superconductors.

The first four lectures of the course will introduce the concept of magnetoelastic coupling with examples of magnetic transitions in oxide minerals such as hematite, ilmenite and magnetite, and will also address the influence of Jahn-Teller and high spin/low spin transitions. Formalities will be based on a revision of Landau theory as set out in the part II core mineralogy course on Strain, Elasticity and Phase Transitions in Minerals. The last two lectures will be in the form of research seminars to illustrate the importance of strain/order parameter coupling, seen from the perspective of elasticity, in examples of colossal magnetoresistance materials and unconventional superconductors.

There will be formal practicals following each of the first four lectures and a more open-ended data handling exercise following on from these. Each student will hand in a report of the data handling exercise, with a maximum limit of 10 pages (font size 12, double line spacing, including figures and references). The deadline for handing in the report will be one week after the final lecture.

Examination: The theory exam (70%) will consist of a 1.5 hour theory paper, with 2 essay questions to be answered out of a total of 3. The practical component (30%) will be an assessment of the reports of the data handling exercise.

MB: Magnetism of Earth and Planetary Materials

Richard Harrison and James Bryson

9 lectures and 3 practicals

Magnetic fields are believed to have played crucial roles in the formation and evolution of the solar system and first planetary bodies. Due to the antiquity, paucity and complexity of terrestrial and extraterrestrial samples dating from this early time, the details of these fields have remained elusive for decades. Thanks to the development of new paleomagnetic techniques and astrophysical observations, we are now starting the understand some aspects of the magnetic history of our own solar system, as well as exoplanetary systems.

The first half of this course (5 lectures, Richard Harrison) builds on the magnetism theory learnt in the Part II Core Mineralogy Course, and applies it to the study of rock magnetism and paleomagnetism of terrestrial and extraterrestrial materials. We provide an introduction to the new science of nanopaleomagnetism: using cutting-edge techniques from physics and materials science to tackle some of the most challenging problems in rock magnetism. The lectures explain how advances in experimental and computational methods are being applied to unlock ancient magnetic signals on Earth and beyond.

The second half of the course (4 lectures, James Bryson) places these new measurements in a broader solar system context, discussing the mechanisms of magnetic field generation within large and small planetary bodies, by the nebula itself, during planetary impacts and by the Sun. We examine 1) the nebula field and its effects on solar accretion and planetary formation; 2) asteroid magnetic fields and what they tell us about the formation, structure and thermochemical state of asteroids; and 3) the long-term evolution of Earths field, and what this means for the thermal history of Earth, plate tectonics and habitability.

The nine lectures are accompanied by three practical sessions, involving the processing, analysis and simulation of magnetic data.

Course Requirements: Part II Core Mineralogy would be an advantage for the 1st half of the course.

Examination: The course will be examined by a 1.5 hour theory exam (80%). Students answer 2 out of a choice of 3 essay style questions. For the remaining 20% of the mark, students produce an assessed written report (1500-2000 words) summarising the results of the 3 practical sessions. The deadline for the report will be 2 weeks after the last practical session.




Past Tripos papers