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Title: Neutron scattering studies of the geometrically frustrated SrLn2O4 materials
Author: Riberolles, Simon Xavier Marie
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2019
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Geometrical frustration in condensed matter is a phenomenon induced by competing magnetic interactions being in a situation of incompatibly with the crystal lattice geometry. In highly frustrated magnets, the competition can be such that a unique magnetic ground state cannot be stabilised, even at the lowest temperatures. Such a situation of instability is known to give rise to unusual and novel properties stimulating our interest for this class of materials. The members of the SrLn2O4 (Ln = Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb) crystalline family, present the characteristics of highly frustrated systems. The magnetic sublattice of these materials consists of interconnected triangular ladders forming a three dimensional distorted honey-comb lattice. This lattice is also bipartite, in a sense that the Ln3+ magnetic ions are hosted by two crystallographically inequivalent sites, resulting in the presence of two different types of magnetic ladders in the system. Many different types of triangular structures are thus combined within these materials, resulting in the strong frustration of the antiferromagnetic Ln3+ exchange interactions. This thesis presents an investigation of the low temperature magnetic properties of the Nd, Gd and Er variants of the SrLn2O4 family. The use of neutron scattering techniques in the determination of the different magnetic orders stabilised by these systems stands as a central aspect of this work. In fact, the structural characteristics of the orders have revealed fundamental aspects of the magnetic properties of this family of material. Of particular interest, it was understood that strong dipolar interaction can stabilise up-down-up-down (udud) N_eel orders progressing along the ladders in SrLn2O4 systems containing the Ln3+ ions bearing the larger magnetic moments. On the other hand, near neighbour antiferromagnetic exchange interactions have the possibility to stabilise right-left-right-left (rlrl) Néel or (rrll) double Néel orders along the ladders, the moments lying within the a - b plane of the materials. An investigation of the low temperature field induced properties of the SrEr2O4 material is moreover proposed in this thesis.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics