Magnetization curves for two-dimensional rectangular lattices of permalloy nanoparticles: experimental investigation and numerical simulation

This work is concerned with the behaviour of a regular 2D rectangular lattice of Ni3Fe nanoparticles, determined by the dipole interaction between them. The samples under study, prepared by electron-beam lithography, consisted of about 10(5) particles approximately 50 nm in size. The magnetization curves were studied by Hall magnetometry for different external magnetic field orientations at 4.2 K and 77 K. The results indicate a collective behaviour of the system. The magnetization curves depend on the external magnetic field direction and temperature; the system exhibits multistability. A model system of interacting 3D magnetic dipoles forming a rectangular lattice was numerically simulated by solving a system of stochastic Landau-Lifshitz equations. The multistability of the system and steps in the magnetization curves were obtained. It is shown analytically that the shape of the magnetization curves depends on the character of the interaction in the system.