Dresden 2009 – wissenschaftliches Programm

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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 Ahsan^1,2, 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].