Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 13: Spinstructures and magnetic Phase Transitions

MA 13.10: Vortrag

Dienstag, 27. März 2007, 12:30–12:45, H5

Magnetic phase diagram of Tb₂PdSi₃ studied by neutron diffraction — •Matthias Frontzek¹, Andreas Kreyssig¹, Mathias Doerr¹, Astrid Schneidewind^1,2, Jens-Uwe Hoffmann³, and Michael Loewenhaupt¹ — ¹TU Dresden, Institut für Festköperphysik, D-01062 Dresden — ²Forschungsneutronenquelle Heinz-Maier-Leibnitz, Lichtenbergerstr. 1, D-85747 Garching — ³Hahn-Meitner-Institut, Glienickerstr. 100, D-14109 Berlin

Tb₂PdSi₃ crystallises in an AlB₂ derived hexagonal structure (space group P6/mmm) yielding a latent geometric frustration for the magnetic Tb³⁺ ions. The anisotropy of the crystal electric field leads to a magnetic easy basal plane with six possible moment directions. The RKKY interaction gives rise to an antiferromagnetic transition at T_N = 23 K. To clarify the microscopic nature of the rich magnetic phase diagram we performed neutron scattering experiments in external magnetic fields up to µ₀H = 6.5 T along the (100) direction.

In zero field we observe an antiferromagnetic long-range ordered (LR) structure with a magnetic unit cell doubled in the basal plane with respect to the chemical unit cell and a (0 0 1/16) propagation along the hexagonal axis. Below 8 K an additional antiferromagnetic short range ordered (SR) structure with a wave vector (0.16 0.16 0.06) appears. The LR propagation changes through two intermediate phases to (0 0 1/4) in the field range 0.1 - 3.0 T. The SR structure seems decoupled from the LR structure and becomes itself long-range ordered around 1.5 T with a propagation (0.13 0.13 0.1) which is further modified to (1/6 1/6 1/4) at fields above 3 T.