# Heteroclinic tangle phenomena in nanomagnets subject to time-harmonic excitations

## Abstract

Magnetization dynamics in uniformly magnetized nanomagnets excited by time-harmonic (AC) external fields or spin-polarized injected currents is considered. The analysis is focused on the behaviour of the AC-excited dynamics near saddle equilibria. It turns out that this dynamics has a chaotic character at moderately low power level. This chaotic and fractal nature is due to the phenomenon of heteroclinic tangle which is produced by the combined effect of AC-excitations and saddle type dynamics. By using the perturbation technique based on Melnikov function, analytical formulas for the threshold AC excitation amplitudes necessary to create the heteroclinic tangle are derived. Both the cases of AC applied fields and AC spin-polarized injected currents are treated. Then, by means of numerical simulations, we show how heteroclinic tangle is accompanied by the erosion of the safe basin around the stable regimes.

- Authors:

- DIETI, Università di Napoli “Federico II,” I-80125 Napoli (Italy)
- Istituto Nazionale di Ricerca Metrologica, I-10135 Torino (Italy)
- Dip. di Ingegneria, Università di Napoli “Parthenope,” I-80143 Napoli (Italy)
- ECE Department and UMIACS, University of Maryland, College Park, Maryland 20742 (United States)

- Publication Date:

- OSTI Identifier:
- 22409975

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Applied Physics

- Additional Journal Information:
- Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHAOS THEORY; COMPUTERIZED SIMULATION; EQUILIBRIUM; EROSION; EXCITATION; FRACTALS; MAGNETIC MATERIALS; MAGNETIZATION; NANOSTRUCTURES; SPIN ORIENTATION

### Citation Formats

```
Serpico, C., Quercia, A., Perna, S., Bertotti, G., Ansalone, P., D'Aquino, M., and Mayergoyz, I.
```*Heteroclinic tangle phenomena in nanomagnets subject to time-harmonic excitations*. United States: N. p., 2015.
Web. doi:10.1063/1.4914530.

```
Serpico, C., Quercia, A., Perna, S., Bertotti, G., Ansalone, P., D'Aquino, M., & Mayergoyz, I.
```*Heteroclinic tangle phenomena in nanomagnets subject to time-harmonic excitations*. United States. doi:10.1063/1.4914530.

```
Serpico, C., Quercia, A., Perna, S., Bertotti, G., Ansalone, P., D'Aquino, M., and Mayergoyz, I. Thu .
"Heteroclinic tangle phenomena in nanomagnets subject to time-harmonic excitations". United States. doi:10.1063/1.4914530.
```

```
@article{osti_22409975,
```

title = {Heteroclinic tangle phenomena in nanomagnets subject to time-harmonic excitations},

author = {Serpico, C. and Quercia, A. and Perna, S. and Bertotti, G. and Ansalone, P. and D'Aquino, M. and Mayergoyz, I.},

abstractNote = {Magnetization dynamics in uniformly magnetized nanomagnets excited by time-harmonic (AC) external fields or spin-polarized injected currents is considered. The analysis is focused on the behaviour of the AC-excited dynamics near saddle equilibria. It turns out that this dynamics has a chaotic character at moderately low power level. This chaotic and fractal nature is due to the phenomenon of heteroclinic tangle which is produced by the combined effect of AC-excitations and saddle type dynamics. By using the perturbation technique based on Melnikov function, analytical formulas for the threshold AC excitation amplitudes necessary to create the heteroclinic tangle are derived. Both the cases of AC applied fields and AC spin-polarized injected currents are treated. Then, by means of numerical simulations, we show how heteroclinic tangle is accompanied by the erosion of the safe basin around the stable regimes.},

doi = {10.1063/1.4914530},

journal = {Journal of Applied Physics},

issn = {0021-8979},

number = 17,

volume = 117,

place = {United States},

year = {2015},

month = {5}

}