Nuclear magnetism and superconductivity : investigations on lithium and rhodium

Juntunen, Kirsi

Nuclear magnetism and superconductivity : investigations on lithium and rhodium

dc.contributor	Aalto-yliopisto	fi
dc.contributor	Aalto University	en
dc.contributor.author	Juntunen, Kirsi
dc.contributor.department	Department of Engineering Physics and Mathematics	en
dc.contributor.department	Teknillisen fysiikan ja matematiikan osasto	fi
dc.contributor.lab	Low Temperature Laboratory	en
dc.contributor.lab	Kylmälaboratorio	fi
dc.date.accessioned	2012-02-17T06:47:00Z
dc.date.available	2012-02-17T06:47:00Z
dc.date.issued	2005-02-19
dc.description.abstract	This thesis describes low temperature experiments on lithium. The experiments concentrate on investigating low temperature phase transitions of two subsystems in this metal: its nuclear spin and electronic systems. These phenomena were investigated in two separate sets of samples, each designed to meet the experimental requirements for the phenomena under investigation. The electronic ground state of lithium at ambient pressures is expected to be superconducting, but earlier experiments show that the metal remains normal at least down to 4 mK. In this thesis research, a lithium sample was cooled down to 0.1 mK, B < 10 nT, but no superconductivity was observed. A new upper limit for the superconducting transition temperature was established, over an order of magnitude lower than the earlier upper limit. Many theoretical estimates predict superconductivity already at higher temperatures, and its absence remains a puzzle. The superconductivity in lithium has been under considerable interest recently, since the superconducting phase was observed in the highly compressed state. The nuclear spin system of lithium was investigated as well. The large magnetic moment of the lithium-7 nuclei made lithium an interesting target for studies of nuclear magnetism. The spin system was cooled down by a two stage adiabatic nuclear demagnetization cryostat. The nuclear magnetic resonance (NMR) spectra, the spin temperature, and the static susceptibility were measured. The NMR spectra revealed the appearance of an anomalous peak at low frequencies. Also, the spin system was found to behave in an irreversible manner at low fields and high nuclear polarizations. These effects give evidence for the existence of a magnetically ordered state of the lithium nuclei. The type of the order was not resolved unambiguously, but some facts point to a ferromagnetic ordering. A tentative phase diagram was constructed for the system. Previously, nuclear magnetism and superconductivity in rhodium metal have been investigated. This thesis also includes some numerical and analytical modeling on the nuclear spin system of rhodium, aimed at the interpretation of the experimental data.	en
dc.description.version	reviewed	en
dc.format.extent	42, [154]
dc.format.mimetype	application/pdf
dc.identifier.isbn	951-22-7487-6
dc.identifier.uri	https://aaltodoc.aalto.fi/handle/123456789/2530
dc.identifier.urn	urn:nbn:fi:tkk-004781
dc.language.iso	en	en
dc.publisher	Helsinki University of Technology	en
dc.publisher	Teknillinen korkeakoulu	fi
dc.relation.haspart	T. A. Knuuttila, J. T. Tuoriniemi, K. Lefmann, K. I. Juntunen, F. B. Rasmussen, and K. K. Nummila. 2001. Polarized nuclei in normal and superconducting rhodium. Journal of Low Temperature Physics 123, numbers 1-2, pages 65-102.
dc.relation.haspart	K. I. Juntunen, K. Lefmann, J. T. Tuoriniemi, and T. A. Knuuttila. 2001. High temperature expansion and exact diagonalization of the rhodium nuclear spin system compared to experimental results. Journal of Low Temperature Physics 124, pages 271-289. [article2.pdf] © 2001 by authors and © 2001 Springer Science+Business Media. By permission.
dc.relation.haspart	J. T. Tuoriniemi, K. I. Juntunen, and J. M. Uusvuori. 2003. Thermal contact to lithium metal. Physica B 329-333, pages 1294-1295. [article3.pdf] © 2003 Elsevier Science. By permission.
dc.relation.haspart	J. T. Tuoriniemi and K. I. Juntunen. 2004. Nuclei in cooperation. Journal of Low Temperature Physics 135, pages 513-543. [article4.pdf] © 2004 by authors and © 2004 Springer Science+Business Media. By permission.
dc.relation.haspart	K. I. Juntunen and J. T. Tuoriniemi. 2005. NMR spectra of highly polarized lithium. Journal of Low Temperature Physics 138, pages 759-764. [article5.pdf] © 2005 by authors and © 2005 Springer Science+Business Media. By permission.
dc.relation.haspart	K. I. Juntunen and J. T. Tuoriniemi. 2004. Nuclear ordering in lithium and an upper limit on its ambient pressure superconducting transition temperature. Physical Review Letters 93, number 15, 157201 : pages 1-4. [article6.pdf] © 2004 American Physical Society. By permission.
dc.relation.haspart	K. I. Juntunen and J. T. Tuoriniemi. 2004. Experiment on nuclear ordering and superconductivity in lithium. Helsinki University of Technology, Low Temperature Laboratory publications, Report 12 (TKK-KYL-012). 52 pages. [article7.pdf] © 2004 by authors.
dc.subject.keyword	lithium	en
dc.subject.keyword	rhodium	en
dc.subject.keyword	ultralow temperatures	en
dc.subject.keyword	nuclear magnetic ordering	en
dc.subject.keyword	nuclear magnetism	en
dc.subject.keyword	superconductivity	en
dc.subject.other	Physics	en
dc.title	Nuclear magnetism and superconductivity : investigations on lithium and rhodium	en
dc.type	G5 Artikkeliväitöskirja	fi
dc.type.dcmitype	text	en
dc.type.ontasot	Väitöskirja (artikkeli)	fi
dc.type.ontasot	Doctoral dissertation (article-based)	en
local.aalto.digiauth	ask
local.aalto.digifolder	Aalto_64632