INFLUENCE OF DIMENSION AND MAGNETIC INTERACTIONS ON ANNIHILATION AND NUCLEATION FIELDS OF PERMALLOY NANODISKS USING MICROMAGNETIC SIMULATIONS

Permalloy can exhibit magnetic vortex configurations depending on their dimensions and geometry, being of great interest due to potential applications in data storage and for cancer treatment. This work focuses on the effects of perpendicular uniaxial anisotropy, dimensions of permalloy nanodisks, and magnetostatic interactions on the annihilation and nucleation fields of magnetic vortices by means of micromagnetic simulations. Nanodisks with different diameters were evaluated, considering the effect of anisotropy generated by a platinum substrate for isolated nanodisks of 20 nm thickness. The effect of magnetostatic interactions for different arrays of identical nanodisks and a 10 x 10 array with random diameters from a normal distribution was also evaluated. The results show that the annihilation and nucleation fields are influenced by the perpendicular uniaxial anisotropy. The higher the anisotropy, the more the annihilation field decreases, and the nucleation field increases, thus favoring the monodomain magnetic configuration. It was also shown that the magnetic interaction between the nanodisks and the lattice geometry led to a variation of the annihilation and nucleation fields. The magnetostatic interaction in the lattice leads to a collective rotation of the magnetic moments, so that the closing of the magnetic flux occurs randomly in a series of nanodisks minimizing the energy.