Correlation Between Spin Configuration and Magnetostatic Interaction of Ferromagnetic Nanocubes

We have investigated three-dimensional (3D) spin configurations of a one-dimensional (1D) array composed of three ferromagnetic nanocubes by means of micromagnetic simulations. In order to modulate the magnetostatic interaction between adjacent nanocuboids, the magnetic field was applied as a controllable external magnetostatic environment. Without any external field, the spin configurations of the asymmetric 3D magnetic vortex structures in each nanocube exhibit identical magnetic chirality. With the increase of the external field, the magnetostatic environment was gradually dominated by the external field, and enhanced the component along field direction of the magnetostatic interaction between nanocuboids, and even accelerated the formation of the cylindrical 3D vortex spin structure at the center of each cuboid lying in the field direction. Interestingly, under a 100 mT field less than the saturation field, the ferromagnetic array exhibited negative magnetic energy, with the three vortex structures occasionally exhibiting opposing chiralities. There was a competitive relationship amongst the shape anisotropy, magnetic energy minimization, and magnetostatic interaction between ferromagnetic nanocuboids, leading to the complex spin configuration and the negative energy phenomenon of the ferromagnetic array.