21 research outputs found
Evidence for Adiabatic Magnetization of cold Dy_N Clusters
Magnetic properties of Dy_N clusters in a molecular beam generated with a
liquid helium cooled nozzle are investigated by Stern-Gerlach experiments. The
cluster magnetizations \mu_z are measured as a function of magnetic field (B =
0 - 1.6T) and cluster size (16 < N < 56). The most important observation is the
saturation of the magnetization \mu_z(B) at large field strengths. The
magnetization approaches saturation following the power law |\mu_z-\mu_0|
proportional to 1/\sqrt{B}, where \mu_0 denotes the magnetic moment. This gives
evidence for adiabatic magnetization.Comment: 4 pages, 3 figure
Magnetism of quantum dot clusters: A Hubbard model study
Magnetic properties of two and three-dimensional clusters of quantum dots are
studied with exact diagonalization of a generalized Hubbard model. We study the
weak coupling limit, where the electrons interact only within a quantum dot and
consider cases where the second or third harmonic oscillator shell is partially
filled. The results show that in the case of half-filled shell the magnetism is
determined by the antiferromagnetic Heisenberg model with spin 1/2, 1 or 3/2,
depending on the number of electrons in the open shell. For other fillings the
system in most cases favors a large total spin, indicating a ferromagnetic
coupling between the dots.Comment: 9 pages, 9 figure