Berlin 2024 – scientific programme

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MA: Fachverband Magnetismus

MA 27: Frustrated Magnets I

MA 27.4: Talk

Wednesday, March 20, 2024, 15:45–16:00, H 2013

On the origin of correlated diffuse scattering in the hexagonal manganites — •Tara Tošić¹, Arkadiy Simonov², and Nicola Spaldin¹ — ¹Materials Theory, ETH Zürich, Switzerland — ²Disordered Materials, ETH Zürich, Switzerland

Using symmetry analysis, first-principles density functional theory and spin dynamics, we pinpoint the origin of the correlated diffuse neutron scattering in hexagonal yttrium manganite (h-YMnO₃). We show that the observed directionality in the structured diffuse scattering in momentum space is a hallmark of the triangular geometry, and that its persistence across a wide range of temperatures, both above and below the Néel temperature, TN, is a result of the strong magnetic frustration. We argue that excitations away from the magnetic ground state - a scenario ruled out in previous modelling attempts - give rise to short-range correlations. Though a hierarchy of nearest-neighbor exchanges and magnetic anisotropy terms, clusters of ordered spins form and interact with each other, creating excitations. We also visualize the magnetic order in terms of composite trimer magnetoelectric monopoles and toroidal moments, rather than individual spins, providing insight into the real space fluctuations, revealing clusters of emerging order in the paramagnetic state, as well as collective short-range excitations in the ordered Néel phase. Our understanding of this directional diffuse scattering both below and above TN provides new insight into the magnetic phase transitions in frustrated systems.

Keywords: multiferroics; frustrated magnetism; local order; correlated disorder; phase transition