  A theoretical analysis of a relation between atomic and spin-electronic
structures for the ground state of single-row aluminum nanowires suspended
between Al(001) electrodes is demonstrated using first-principles
molecular-dynamics simulations. We obtain a unusual result that a
3-aluminum-atom nanowire sandwiched between the electrodes does not manifest
magnetic ordering although an isolated aluminum trimer molecule in a straight
line is spin-polarized. On the other hand, a 5-atom nanowire exhibits
ferromagnetic ordering, where three central atoms form a spin-polarized trimer.
Moreover, in the case of an 8-atom nanowire, the middle atoms in the nanowire
form two spin-polarized trimers with antiferromagnetic ordering.
