Münster 1999 – wissenschaftliches Programm

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AM: Magnetismus

AM 10: Postersitzung

AM 10.67: Poster

Dienstag, 23. März 1999, 16:15–20:00, F\"urstenberghaus

Finite Size Effect of Magnetic Dot Arrays — •R. Hassdorf¹, K. Shigeto¹, T. Ono², and T. Shinjo¹ — ¹Institute for Chemical Research, Kyoto University, Japan — ²Faculty of Science & Technology, Keio University, Yokohama, Japan

We report on the magnetic switching behavior of a series of periodic arrays of 3 × 3 square submicrometer dots of permalloy fabricated via electron-beam lithography and lift-off technique. Hysteresis loops measured by SQUID magnetometry with the applied field aligned parallel to an array edge and along a diagonal, respectively, reveal distinct features of a finite size effect: (i) While the loop shape observed for an extended dot lattice points to a magnetic fourfold anisotropy which can be attributed to an anisotropic dipole-dipole interaction between magnetically unsaturated parts of the dots [1], here, any signature of a significant anisotropy is lacking in the magnetization measurements. However, ferromagnetic resonance experiments are in progress to provide more accurate information on this aspect. (ii) The applied field orientation has a profound effect on the magnetization reversal with the shape of the hysteresis loop becoming more complex when the field is aligned along an array diagonal. Details of this process will be discussed with reference to recent micromagnetic simulations [2].

[1] C. Mathieu et al., Appl. Phys. Lett. 70, 2912 (1997)

[2] R. L. Stamps et al., J. Magn. Magn. Mater. 177-181, 813 (1998)