Speaker
Description
In this presentation, we will explore the complex magnetic behaviour of Ho-doped langasite ([La$_{1−x}$Ho$_x$]$_3$Ga$_5$SiO$_{14}$), focusing on understanding how local structural distortions influence the ising-like Ho3+ moments and ultimately the macroscopic magnetoelectric properties. The study leverages complementary experimental evidence, combining polarised neutron diffraction and angular-dependent magnetisation measurements to precisely determine the atomic site susceptibility tensor and reconcile it within the constraints of the local-ionic and global symmetries. The analysis incorporates a novel framework that models the orientations of the Ho3+ ising axes, along with symmetric rotations around the trigonal $C_3$ axis that restore the global $P312$ symmetry, despite the presence of broken local $C_2$ symmetry. The conclusions provide insights into the interplay between local distortions, magnetic anisotropies and macroscopic magnetic and magnetoelectric behaviour, underscoring the importance of polarised neutron diffraction in resolving subtle magnetic features that are otherwise obscured in complex materials such as multiferroics and other systems with strong spin-lattice coupling.
