High-resolution magnetic imaging by local tunneling magnetoresistance |
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Authors: | W Wulfhekel HF Ding W Lutzke G Steierl M Vázquez P Marín A Hernando J Kirschner |
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Institution: | (1) Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany, DE;(2) Instituto de Magnetismo Aplicado, Apartado de Correos 155, 28230 Las Rozas, Madrid, Spain, ES |
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Abstract: | We give an overview over our recent efforts of high-resolution magnetic imaging using scanning tunneling microscopy with a
ferromagnetic tip. Magnetic sensitivity is obtained on the basis of local tunneling magnetoresistance between a soft magnetic
tip and the sample. The magnetisation of the tip is switched periodically with a small coil, leading to variations of the
tunneling current due to the tunneling magnetoresistance effect. These variations are detected with a lock-in amplifier to
separate spin-dependent parts from the topographic parts of the tunneling current such that the topography and the magnetic
structure of the sample can be recorded simultaneously. Crucial for this method is to avoid mechanical vibrations of the tip,
that may also lead to variations in the tunneling current. Exemplary studies of polycrystalline Ni and the closure domain
pattern of Co(0001) are presented, showing high contrast at acquisition times as low as 3 ms/pixel and a lateral resolution
of the order of 1 nm. Further it is demonstrated that besides topography and magnetisation, also local information about the
magnetic susceptibility can be obtained.
Received: 28 April 2000 / Accepted: 15 May 2000 / Published online: 7 March 2001 |
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Keywords: | PACS: 75 60 Ch 75 30 Pd 75 50 Kj |
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