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MA: Magnetismus

MA 28: Invited Talks Brune / Moritz

MA 28.1: Hauptvortrag

Donnerstag, 30. März 2006, 14:00–14:30, HSZ 03

Surprises in the Magnetism of Surface Supported Nanostructures — •Harald Brune — EPFL, CH-1015 Lausanne

We use self-assembly during atomic beam epitaxy to create two-dimensional metallic islands with sizes from a few thousands of atoms down to the single atom limit. We show how the magnetic properties, such as anisotropy energy, spin- and orbital moments, as well as spin-polarization, evolve as function of size. Measurements with Magneto-Optical Kerr Effect (MOKE), X-ray Magnetic Circular Dichroism (XMCD), and STM reveal a giant increase in anisotropy with reduced coordination. As a consequence, the low-coordinated atoms are at the origin of magnetic anisotropy in nanostructures on single crystal surfaces. We present model systems exploring the ultimate density limit of magnetic information storage. They are characterized by uni-axial out-of-plane magnetization, narrow anisotropy distributions, and the absence of dipolar interactions. Spin-polarized STM measurements show up to 850% tunnel magnetoresitance (TMR) and 80% spin-polarization on single domain islands.