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Title: High pressure study of magnetic quantum phase transitions in transition metal materials
Author: Harrison, Christopher
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2013
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In this thesis magnetic materials are tuned towards quantum critical points by the application of hydrostatic pressure. A novel method for measuring magnetic susceptibility in a Bridgman anvil cell is developed, which allows for counterwound detection and compensation coils to be located within the sample space. This enables magnetic susceptibility to be measured up to 20 GPa with excellent signal to noise ratios. This technique along with electrical transport measurements have been used to study three magnetic d-metal materials. FePt3 which shows two antiferromagnetic transitions at ambient pressure has been found to be very weakly pressure dependent. A pressure study of Mo3 Sb7 , a superconducting material with additionally reported antiferromagnetic order has shown an increase in the superconducting transition temperature from Tc = 2.1 ± 0.1 K at zero pressure to Tc = 3.4 ± 0.1 K at the highest pressure measured of 8.5 GPa. Measurements of single crystals of NbFe2 under pressure have shown good agreement between the pressure phase diagram and the chemical composition phase diagram. A ratio for chemical substitution to pressure was determined to be 2.4 ± 0.1 ∗ 10−3 (%Nb)GPa−1 . In the temperature dependence of the electric resistivity above 4 K non Fermi liquid type behaviour is seen over all pressures measured, up to the maximum pressure of 13 GPa.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available