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MA: Fachverband Magnetismus
MA 36: Magnetic Particles and Clusters II
MA 36.7: Vortrag
Donnerstag, 26. März 2009, 16:45–17:00, HSZ 401
Antiferromagnetic finite nanowires: Heisenberg spin model revisited — •Mohammed Ahsanul Hoda Ahsan1,2, Jamal Berakdar1, and Mohammed Mahfoozul Haque2 — 1Institute of Physics, Martin-Luther University, Halle-Wittenberg, Heinrich-Damerow Str.-4, 06120 Halle, Germany. — 2Department of Physics, Jamia Millia Islamia(Central University), New Delhi 110025, India.
In line with a recent experimental work on antiferromagnetic finite nanowires[1] and its subsequent theoretical discussions[2,3], we present here exact diagonalization calculations on the one-dimensional antiferromagnetic Heisenberg spin-1/2 chain on a magnetic substrate. The chain-substrate coupling Γ is assumed to be ferromagnetic. Numerical diagonalization is performed for chains of up to 25 spins to find the ground state and the first five excited states. The critical value of Γ at which the ground state first changes its spin symmetry is found to be consistently higher for the odd chains as compared to the even chains considered. In odd chains, the ground state and the first excited state have the same total spin equal to 1/2 whereas for even chains the ground state and the first excited state have spins 0 and 1 respectively. These bring in the premise of an odd-even effect on the ground state and low lying excited states of finite antiferromagnetic nanowires.
[1] C. F. Hirjibehedin, C. P. Lutz, A. J. Heinrich, Science 312, 1021(2006).
[2] S. Lounis, P. H. Dederichs, and S. Blugel, Phys. Rev. Lett. 101, 107204(2008).
[3] P. Politi and M. G. Pini, arXiv:0811.1687v1 [cond-mat.mtrl-sci].