Magnetic Properties Of Small Clusters Research Articles

Probing buried magnetic nanostructures by spin-resolved local density of states at the surface: A density functional study

We demonstrate that it is possible to resolve magnetic properties of small clusters buried up to 1.5 nm deep beneath a metallic surface. The possibility of deducing magnetic properties of buried nanostructures by studying polarization maps of the surface is discussed. Moreover, we show that there is a way to determine the coupling of buried structures to each other by studying the polarization of electrons in vacuum space above the system.

Exact diagonalization of Hubbard clusters at finite temperatures

Finite temperature electronic and magnetic properties of small clusters are investigated in the framework of the Hubbard model by using exact diagonalization methods and by sampling the different cluster topologies exhaustively. Results are discussed for the specific heat C(T), magnetic susceptibility χ(T), local magnetic moments μi(T), average magnetic moments \(\overline\mu_N(T)\)and spin-correlation functions γij(T). Representative cluster sizes and band-fillings are considered showing antiferromagnetic-like (AF) and ferromagnetic-like (FM) behaviors. For half-band filling ν= N the susceptibility shows an AF high-temperature behavior of the form χ≈1/(T + TN) from which the cluster `Neel’ temperature TN is derived. In contrast, for ν= N + 1 a FM high-temperature behavior of the form χ≈1/(T - TC) is found, where TC can be interpreted as the cluster `Curie’ temperature. In both cases one also observes peaks in C(T), either at T≃TN or T≃TC, which reflect the development of spin fluctuationsand the breakdown of the low-temperature short-range magnetic order. The dependence of TN and TC on cluster size N and interaction strength U/t is analyzed in terms of effective Heisenberg spin interactions. Finally, the effects of temperature-induced structural fluctuations are discussed.

Magnetic properties of small clusters as function of the geometry

Magnetic properties of small clusters as function of the geometry

Magnetic properties of small clusters as function of the geometry

Abstract The magnetic properties of the ground state of one- and two-dimensional small clusters (Na=16 sites) are studied solving exactly the Heisenberg Hamiltonian. We are interested in studying the magnetic behavior as a function of the lattice geometry. The total spin S shows an interesting behavior as a function of the ferromagnetic (antiferromagnetic) exchange interaction J1>0 (J2

Calculation of finite temperature magnetic properties of clusters

The finite temperature magnetic properties of small clusters having N⩽6 atoms are determined in the framework of the single-band Hubbard model by using exact diagonalization methods and by taking into account both electronic and structural excitations. Results are given for the average magnetic moment 〈S〉 and for the spin correlation function 〈Si⋅Sj〉. The temperature dependence in weakly, intermediate, and strongly interacting regimes is analyzed and the role of temperature-induced structural changes is discussed.

The structures and magnetic properties of small clusters

The geometric structures and magnetic properties of small clusters have been studied by using a linear combination of atomic orbitals approach with the density functional formalism, and the Kohn - Sham equation is solved self-consistently by the discrete variational method. It is found that it is favourable for the B atom to locate at the surface, not at the centre of the cluster, and that the tetrahedron for and the triangular prism for clusters are not the most stable structures. When one atom in an cluster is replaced by a B atom, forming an cluster, the binding energy increases, while the moment of the Fe atom decreases. It is indicated that the environment and doping play important roles as regards the stability and magnetic properties of clusters.