Reply to the comment on the paper "Thermodynamics of two-dimensional magneto nanoparticles (P. Vargas, D. Altbir, M.Knobel and D. Laroze)" by H. Buettner and Yu. Gaididei

It is shown that there is bi-stability in a two dimensional system consisting of non interacting magnetic nanoparticles with equal uniaxial anisotropies. It is also shown that bi-stability still remains in three dimensions. The only consideration is that the applied magnetic field has to be perpendicular to the anisotropy axis.