Emergence of magnetic order in the Rare Earth Intermetallic PrPtAl
Item statusRestricted Access
Embargo end date31/12/2100
Abdul-Jabbar, Gino Jamal
Magnetism of the rare earth intermetallics present some of the most important challenges for understanding correlated electron systems . In this thesis I distil this immense challenge, to understanding the unusual magnetic properties of the rare earth intermetallic PrPtAl. At first glance, PrPtAl appears to be a typical local f moment system, where the electronic states of Pr3+ are composed of nine singlet states, split by the crystal electric field for the J = 4 spin-orbit state in low crystal symmetry (orthorhombic, Pnma). The absence of a magnetic ground state would naively lead us to expect PrPtAl to be a simple paramagnet, but the results from this thesis show that the material is more complex, ordering magnetically at 5.7 K in spite of its singlet ground state. This thesis investigates the emergence of magnetic order in PrPtAl. For this purpose, the properties of PrPtAl were measured using high quality single crystals grown using the Czochralski technique. These crystals were used to measure: bulk properties at the Centre for Science at Extreme Conditions (CSEC, University of Edinburgh) and to perform neutron and x-ray magnetic scattering experiments at central facilities within Europe (ISIS, ESRF) and North America (NCNR). The results of this thesis conclusively show that PrPtAl does not directly realise ferromagnetism, but initially orders into two modulated magnetic states between 5.7-5.2 K and 5.2-4.7 K. These states cannot be explained using a simple local moment picture, but appear to be driven by a complex interaction between local moments and conduction electrons, in a possible quantum order-by-disorder type mechanism.