We have used a new type of torque magnetometer: a piezoresistive cantilever. It detects the force and torque applied to the end of the cantilever beam by changes in its resistance. We report the first use of this device at temperatures below 1 K. We observed a hysteretic behavior of the resistance at low magnetic field (less than 10 mT) in that temperature range. At higher field it has a smoothly varying magnetoresistance which permitted us to measure the de Haas-van Alphen (dHvA) effect in two superconductors: $ kappa$-(BEDT-TTF)$ sb2$Cu(NCS)$ sb2$ and Sr$ sb2$RuO$ sb4.$ These measurements demonstrated that a large excitation current can be used if the sample is well thermalized but that torque interactions (TI) can affect the signal. TI can be reduced by the use of feedback. We also present measurements above 75 K of $H sb{c1}$ of YBa$ sb2$Cu$ sb3$O$ sb{6.9}$ obtained by modulating the field and measuring the torque signal at an harmonic of the modulation frequency.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.27545 |
| Date | January 1997 |
| Creators | Lupien, Christian. |
| Contributors | Taillefer, Louis (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001618643, proquestno: MQ37143, Theses scanned by UMI/ProQuest. |
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