Microcalorimetry In Pulsed Magnetic Fields
Lead Research Organisation:
University of Bristol
Department Name: Physics
Abstract
High magnetic field measurements of the electronic properties of materials have produced seminal breakthroughs which have transformed science. These advances, such as the quantum Hall effects were made by measuring electrical transport (resistivity, Hall effect etc). Thermodynamic probes have unique capabilities as they can reveal quantum states hidden to other probes but these are rarely attempted at very high fields because of the technical difficulties with performing them. Here we propose to develop a new generation device for measuring specific heat in very high pulsed magnetic fields, and a complementary low-cost device for creating such fields inside a laboratory environment.
The use of pulsed fields would make a step-change in capability for heat-capacity studies of quantum materials, as it would greatly increase the maximum range of magnetic field-space thus allowing previously out of reach transitions to be studied. Importantly, it will also reduce enormously the carbon footprint /cost of the measurement. This new capability will allow us to study the evolution of entropy to unprecedented high fields and thus get new insights into the nature of field-induced states, such as the normal state of high temperature superconductors or quantum critical magnetic transitions.
To give affordable access to magnetic fields above 50T, we will also develop a micro-pulsed magnetic field apparatus. This will enormously increase access to high fields, increasing productivity of researchers and meaning expensive experiments in international facilities will be better prepared. Many break-through, high field discoveries are serendipitous, for example integer and fractional quantum Hall effects and quantum oscillations in high temperature superconductors. So more widespread use of high magnetic field will make such breakthroughs more likely.
The use of pulsed fields would make a step-change in capability for heat-capacity studies of quantum materials, as it would greatly increase the maximum range of magnetic field-space thus allowing previously out of reach transitions to be studied. Importantly, it will also reduce enormously the carbon footprint /cost of the measurement. This new capability will allow us to study the evolution of entropy to unprecedented high fields and thus get new insights into the nature of field-induced states, such as the normal state of high temperature superconductors or quantum critical magnetic transitions.
To give affordable access to magnetic fields above 50T, we will also develop a micro-pulsed magnetic field apparatus. This will enormously increase access to high fields, increasing productivity of researchers and meaning expensive experiments in international facilities will be better prepared. Many break-through, high field discoveries are serendipitous, for example integer and fractional quantum Hall effects and quantum oscillations in high temperature superconductors. So more widespread use of high magnetic field will make such breakthroughs more likely.
Organisations
People |
ORCID iD |
| Antony Carrington (Principal Investigator) |
| Description | The main goal of this project was to test a new way to measure the specific heat of materials at low temperatures (below 20K) in a pulsed magnetic field, for example, those available at the European Magnetic Fields Laboratory in Toulouse. The technique relied on depositing a thermometer directly on to a single crystal sample with the goal of achieving a very high thermal response rate due to the very low mass the thermometer. The fabrication procedure for the thermometers (made from a germanium-gold alloy) was optimized and a process for insulating the thermometer from the sample was found. We found however, that a fastest response rate achieved was around 1 millisecond at a temperature of 4K. This indicates that despite the very low mass of the thermometer, the thermal coupling to the samples was too poor for a higher response rate to be achieved (we were aiming for a response rate about 100 times faster than this). The device was tested in a pulsed field system in Toulouse. Although, the noise performance was adequate, considerable heating of the sample was observed during the magnetic field pulse, again indicating that insufficient thermal coupling was achieved. Our conclusions were that the fabrication process investigated in this project was not good enough to achieve a working calorimeter for pulsed magnetic field set ups. Further work is required to better optimize the thermal coupling, which unfortunately was not possible during this short duration (18 months) New Horizons project. |
| Exploitation Route | The work did not achieve a working calorimeter so there is limited use by others, apart from identifying what does not work. |
| Sectors | Other |