Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 23: Micro- and Nanostructured Magnetic Materials III
MA 23.5: Vortrag
Donnerstag, 25. März 2010, 11:15–11:30, H3
Ground state and magnetization reversal of spin ice patterns — •Alexandra Schumann1, Björn Sothmann2, Philipp Szary1, and Hartmut Zabel1 — 1Experimentalphyik IV, Ruhr-Universität Bochum, 44780 Bochum, Germany — 2Theoretische Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany
We present experimental realizations of magnetic dipole arrays on honeycomb lattices and discuss the remanent state as well as the magnetization reversal in an external field parallel to the main symmetry directions. Because of the large shape anisotropy, the ground state can only be reached by driving the system through minor loops. The nanostructures were prepared by means of e-beam lithography and the dipole configurations were imaged by magnetic force microscopy (MFM) at room temperature. They consist of Fe-bars with dimensions length, width and thickness of 3000 nm, 300 nm, and 20 nm, respectively. Here we discuss three honeycomb patterns with inter island distances of 400 nm, 800 nm and 1700 nm. For large dipolar separation we observe a nearly uncorrelated ground state with the frequency of type I (three in or three out) and type II (two in - one out, or two out - one in) vertices as expected for random distribution. For short separations between the dipoles the system is highly correlated with a predominance of type II states, but due to defects in the lattice also type I states are present. Further investigations, including the application of magnetic fields in different directions with respect to the main symmetry axes are currently being performed. This work is supported by DFG-SFB 491, which is gratefully acknowledged.