Numerical simulations of collective magnetic properties and magnetoresistance in 2D ferromagnetic nanoparticle arrays

Abstract

Magnetic properties and magnetoresistance (MR) in 2D magnetic nanoparticle (NP) arrays are investigated by solving the Landau–Lifshitz–Gilbert equation at T = 0 K. The interparticle interactions induce a decrease in the coercive field and in the MR amplitude compared with the non-interacting case, while in some cases, the variation of the remanent magnetization is found to be non-monotonic when increasing the dipolar strength. For different values of the anisotropy, these variations of the coercive field, the remanent magnetization and the MR ratio are reproduced and exhibit a scaling on the dipolar/anisotropy ratio. These results suggest that the magnetic properties of the assemblies can be described by an individual or collective behaviour depending on the balance between the magnetic anisotropy and the dipolar interactions. In the case of strongly interacting NPs, the corresponding configurations of the magnetic moments at the remanent state reveal the formation of a ferromagnetic order at moderate dipolar strength (increase in the remanent magnetization) while small ferromagnetic domains/chains coupled antiferromagnetically are obtained in the case of strongly interacting NPs (decrease in the remanent magnetization). Such domains lead to a reduction in the MR amplitude and to a deviation from the m2-law in the resistance-magnetic field [R(H)] characteristic of the non-interacting case.

Increase of magnetic hyperthermia efficiency due to dipolar interactions in low-anisotropy magnetic nanoparticles: Theoretical and experimental results

“…To illustrate it, we have p erformed simu lations based on the solvin g of the LLG equation at T = 0 K. Sin gle-domain NPs are p laced on a square lattice and carry macrospins considered as magnetic p oint dip oles. M ore details on the resolution can b e found in Ref [19]. In the present study , the following p arameters have been consid ered: MS = 2 ×10 6 A m -1 , D = 13 nm, the center-to-center interparticle distance was 15 nm, and the individual anisotropy K ind of the nanop articles was varied.…”

“…Details on the mod el used and results on the influence of magnetic interactions on the magnetic and magnetotransp ort p rop erties of 2D isotrop ic assemblies of M NPs can be found in Ref. [19].…”

Ferrimagnetic nanocrystal assemblies as versatile magnetic particle hyperthermia mediators

“…37 Eventually, we may surmise that each nanocluster behaves as a ferrimagnetic coherent region of aligned correlated particles whose magnetic moment follows the external magnetic field with tunable convenience. 38 What follows is how these magnetostructural features of colloidal nanocrystal clusters correlate with magnetic hyperthermia measurements.…”

Role of the poly-dispersity and the dipolar interaction in magnetic nanoparticle systems: Monte Carlo study

“…Besides, studying fundamental properties of nanostructure magnetic materials is an interesting problem. In fact, the number of papers performing simulations of magnetic nanoparticle systems has increased fast during this decade [5][6][7][8][9][10][11][12][13][14][15][16][17]. However, these papers seemed to focus on the anisotropy and interparticle interactions, while the experiments proved that the size distribution has the prime importance [18].…”