High Pressure Study of Magnetic Quantum Phase Transitions in Transition Metal Materials

Christopher Harrison

Research output: ThesisDoctoral Thesis

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In this thesis magnetic materials are tuned towards quantum critical points by the appli-
cation of hydrostatic pressure. A novel method for measuring magnetic susceptibility in a
Bridgman anvil cell is developed, which allows for counterwound detection and compen-
sation 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 su-
perconducting material with additionally reported antiferromagnetic order has shown an
increase in the superconducting transition temperature from Tc = 2.1 ± 0.1 K at zero pres-
sure 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 substi-
tution to pressure was determined to be 2.4 ± 0.1 ∗ 10−3 (%Nb)GPa−1 . In the tempreture
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.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Niklowitz, Philipp, Supervisor
Award date1 Aug 2013
Publication statusUnpublished - 2013

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