title: Density functional theory study of magnetic coupling in the Gd12O18 cluster.
abstract: The magnetic properties of the Gd(12)O(18) cluster cut from the bulk Gd(2)O(3) crystal are investigated using the spin-polarized density functional theory within the broken-symmetry approach. Our work reveals that in the ground state of the cluster the antiferromagnetic coupling between adjacent Gd (4f(7)) spins is preferred energetically. This result is in contrast to a recent prediction made by Pedersen and Ojamae (Pedersen, H.; Ojamae, L. Nano Lett. 2006, 6, 2004) but is consistent with recent experimental observations. The optimized structures of the cluster in the lowest-energy broken-symmetry state and the highest-spin ferromagnetic state are almost identical. The latter state is 71.5 cm(-1) higher in energy than the former one, giving a value of about -0.24 cm(-1) for the magnetic coupling constant, which is comparable to that estimated from experiments on the bulk crystal. The relative energies of various 4f(7) spin patterns of the cluster are calculated, and certain characteristics of the cluster in the lowest-energy broken-symmetry state are discussed.
authors.affiliation: Department of Physics, Anhui Normal University, Wuhu, Anhui, 241000, People's Republic of China. ninglx@mail.ahnu.edu.cn
authors.forename: Lixin
authors.initials: L
authors.lastname: Ning
authors.forename: Yongfan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Cui
authors.forename: Mario Italo
authors.initials: MI
authors.lastname: Trioni
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Brivio