A. Ghazali

Magnetic susceptibility and valency state in Sm3S4

Abstract The lack of pronounced temperature dependence in the magnetic susceptibility of Sm3S4 rules out a magnetic ground state for Sm ions. Comparison with semiconducting and metallic phases of SmS suggest the presence of one Sm2+ ion for two non-integral valency Sm ions.

Dipolar Effects in Magnetic Nanostructures

The medium scale magnetic arrangement of nanostructures results from the competition of long ranged interactions such as dipolar ones with short ranged interactions such as exchange and anisotropy. A brief report of the experimental situation and of related numerical simulations is given with attention to the specific patterns such as vortices and pin-shaped domains which are observed in nanostructures. A new method of determining the magnetic ground state of a 2D nanostructure is reported. The indirect influence of the lattice symmetry on the magnetic symmetry by means of long ranged interactions is demonstrated to occur as observed experimentally. Different approximate solutions of the ground state equation are classified according to their level of approximation with evidence for topological defects such as vortices, spirals and labyrinths as metastable solutions in 2D samples. Vortices are shown to be stable in nanostructures. The relative stability of pin-shaped domains is demonstrated.