# Dresden 2017 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 44: PhD Symposium Quantum Magnets (contributed talks)

### MA 44.4: Vortrag

### Mittwoch, 22. März 2017, 15:45–16:00, HSZ 403

**Magnetic correlations in artificial xy spin systems** — •Naëmi Leo^{1}, Oles Sendetskyi^{1}, Dominik Schildknecht^{1}, Peter Derlet^{1}, Stefan Holenstein^{1}, Hubertus Luetkens^{1}, Stephen Lee^{2}, and Laura J. Heyderman^{1} — ^{1}Paul Scherrer Institute, Villigen, Switzerland — ^{2}St. Andrews University, St. Andrews, Scotland

The coupling of continuous spin degrees of freedom on two-dimensional lattices can give rise to interesting phenomena such as the topological Kosterlitz-Thouless transition. A model system to study the influence of external parameters on the magnetic order can be emulated by controlled arrangements of nanomagnets coupled via dipolar interactions. Using electron beam lithography periodic arrangements of circular dots with diameters in the order of a few tens of nanometers can be patterned. Due to the circular shape of the magnetic dots, the resulting macrospin resembles a freely-rotating in-plane xy moment.

Here, we investigate the thermal behaviour and onset of magnetic correlations of fluctuating, interacting xy moments on a square lattice using low-energy muon spin relaxation (muSR), which is a highly sensitive probe for magnetic fields and fluctuations. While the magnetic dynamics of non-interacting xy moments are described by one time scale determined by the superparamagnetic blocking, strongly interacting macrospins develop partial static order at temperatures where non-interacting single particles still fluctuate. In this regime, the dynamics are described by two time scales related to the strong correlations due to a cooperative phase transition.