Monte Carlo calculations on the magnetization profile and domain wall structure in bulk systems and nanoconstricitons

A Monte Carlo algorithm suitable to study systems described by an anisotrop ic Heisenberg Hamiltonian is presented. This technique has been tested succ essfully with 3D and 2D systems, illustrating how magnetic properties depen d on the dimensionality and the coordination number. We have found that mag netic properties of constrictions differ from those appearing in bulk. In p articular, spin fluctuations are considerable larger than those calculated for bulk materials. In addition, domain walls are strongly modified when a constriction is present, with It decrease of the domain-wall width. This de crease is explained in terms of previous theoretical works.