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Title: '3He films adsorbed on graphite : NMR and heat capacity down to below 1 mK.
Author: Siqueira, Marcio Lhamas De.
ISNI:       0000 0004 2666 5940
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1995
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3He films adsorbed on graphite were studied down to temperatures below 1 mK using nuclear magnetic resonance (NMR) and heat capacity as probes. This is the first work that combined heat capacity and NMR in the same cell. The substrate used was Grafoil, a form of exfoliated graphite. Continuous wave NMR was measured using conventional Q-meter circuits, whereas heat capacity was measured using the standard adiabatic method. Thermometry was based on a melting curve thermometer, which served as the primary thermometer. A platinum pulsed NMR and a lanthanum diluted cerium magnesium nitrate (LCMN) thermometers, both calibrated against the melting curve thermometer were also employed. The work focused mainly in the study of the nuclear magnetism when the film is in a solid phase. For pure 3He films, submonolayer and second layer films were investigated. Here, it was observed that the Heisenberg model is appropriate to describe both nuclear magnetic susceptibility and heat capacity of this system. However, the discrepancies in the exchange constants inferred from the different experimental probes are attributed to multiple spin exchange effects, in line with what has been observed in bulk solid 3He. Another system studied in this work was 3He adsorbed on two layers of deuterium hydride (HD) preplated graphite. In this case, a cusp in the susceptibility at a temperature of 1 mK, interpreted as indicative of a magnetic phase transition, was a particularly intriguing observation
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Thermometry