Next weeks' seminar at ICTP

[CM ICTP - Trieste]

									07/01

JOINT ICTP/SISSA CONDENSED MATTER SEMINARS
Academic Year 2006/07


Seminar Room - Main Building  (first floor)



Wednesday, 21 February -     4:00 p.m.



R. WIESENDANGER  ( University of Hamburg )



"Mapping spin structures on the atomic scale"


Abstract

A fundamental understanding of magnetic and spin-dependent phenomena 
requires the determination of spin structures and spin excitations down 
to the atomic scale. The direct visualization of atomic-scale spin 
structures [1-4] has first been accomplished for magnetic metals by 
combining the atomic resolution capability of Scanning Tunnelling 
Microscopy (STM) with spin sensitivity, based on vacuum tunnelling of 
spin-polarized electrons [5]. The resulting technique, Spin-Polarized 
Scanning Tunnelling Microscopy (SP-STM), nowadays provides 
unprecedented insight into collinear and non-collinear spin structures 
at surfaces of magnetic nanostructures and has already led to the 
discovery of new types of magnetic order at the nanoscale [6]. More 
recently, the detection of spin-dependent exchange and correlation 
forces has allowed a first direct real-space observation of spin 
structures at surfaces of antiferromagnetic insulators [7]. This new 
type of scanning probe microscopy, called Magnetic Exchange Force 
Microscopy (MExFM), provides a powerful new tool to investigate 
different types of spin-spin interactions based on direct-, super-, or 
RKKY-type exchange down to the atomic level. By combining SP-STM with 
inelastic electron tunnelling spectroscopy or by performing MExFM 
together with high-precision measurements of damping forces localized 
or confined spin excitations in magnetic systems of reduced dimensions 
now become experimentally accessible.

References
[1]	R. Wiesendanger, I. V. Shvets, D. Bürgler, G. Tarrach, H.-J. 
Güntherodt, J. M. D. Coey, and S. Gräser, Science 255, 583 (1992);
	R. Wiesendanger, I. V. Shvets, D. Bürgler, G. Tarrach, G. Güntherodt, 
H.-J. Güntherodt, and J. M. D. Coey, Europhys. Lett. 19, 141
	(1992)
[2]	S. Heinze, M. Bode, O. Pietzsch, A. Kubetzka, X. Nie, S. Blügel, 
and R. Wiesendanger, Science 288, 1805 (2000)
[3] 	A. Kubetzka, P. Ferriani, M. Bode, S. Heinze, G. Bihlmayer, K. von 
Bergmann, O. Pietzsch, S. Blügel, and R. Wiesendanger, Phys. Rev.
	Lett. 94, 087204 (2005)
[4] M. Bode, E. Y. Vedmedenko, K. von Bergmann, A. Kubetzka, P. 
Ferriani,  S. Heinze, and R. Wiesendanger, Nature Materials 5, 477 
(2006)
[5]	R. Wiesendanger, H.-J. Güntherodt, G. Güntherordt, R. J. Gambino, 
and R. Ruf, Phys. Rev. Lett. 65, 247 (1990)
[6]	 K. von Bergmann, S. Heinze, M. Bode, E. Y. Vedmedenko, G. 
Bihlmayer,   S. Blügel, and R. Wiesendanger, Phys. Rev. Lett. 96, 
167203
	(2006)
[7]   	U. Kaiser, A. Schwarz, and R. Wiesendanger, Nature (2007), in 
press