# Noise-induced bifurcations in magnetization dynamics of uniaxial nanomagnets

## Abstract

Stochastic magnetization dynamics in uniformly magnetized nanomagnets is considered. The system is assumed to have rotational symmetry as the anisotropy axis, the applied field, and the spin polarization are all aligned along an axis of symmetry. By appropriate integration of the Fokker-Planck equation associated to the problem, the stochastic differential equation governing the evolution of the angle between the magnetization orientation and the symmetry axis is derived. The drift terms present in this equation contain a noise-induced drift term, which, in combination with drift terms of deterministic origin, can be written as the derivative of an effective potential. Superparamagnetic-like transitions are studied in connections with the bifurcations of the effective potential as temperature and excitation conditions are varied.

- Authors:

- Dipartimento di Ingegneria Elettrica e delle Tecnologie dell'Informazione, Università di Napoli “Federico II,” I-80125 Napoli (Italy)
- Istituto Nazionale di Ricerca Metrologica, I-10135 Torino (Italy)
- Dipartimento 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:
- 22403041

- 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:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANISOTROPY; EXCITATION; FOKKER-PLANCK EQUATION; MAGNETIC MATERIALS; MAGNETIZATION; MAGNETS; POTENTIALS; SPIN ORIENTATION; STOCHASTIC PROCESSES; SUPERPARAMAGNETISM; TEMPERATURE DEPENDENCE

### Citation Formats

```
Serpico, C., E-mail: serpico@unina.it, Perna, S., Quercia, A., Bertotti, G., D'Aquino, M., and Mayergoyz, I. D.
```*Noise-induced bifurcations in magnetization dynamics of uniaxial nanomagnets*. United States: N. p., 2015.
Web. doi:10.1063/1.4906961.

```
Serpico, C., E-mail: serpico@unina.it, Perna, S., Quercia, A., Bertotti, G., D'Aquino, M., & Mayergoyz, I. D.
```*Noise-induced bifurcations in magnetization dynamics of uniaxial nanomagnets*. United States. doi:10.1063/1.4906961.

```
Serpico, C., E-mail: serpico@unina.it, Perna, S., Quercia, A., Bertotti, G., D'Aquino, M., and Mayergoyz, I. D. Thu .
"Noise-induced bifurcations in magnetization dynamics of uniaxial nanomagnets". United States. doi:10.1063/1.4906961.
```

```
@article{osti_22403041,
```

title = {Noise-induced bifurcations in magnetization dynamics of uniaxial nanomagnets},

author = {Serpico, C., E-mail: serpico@unina.it and Perna, S. and Quercia, A. and Bertotti, G. and D'Aquino, M. and Mayergoyz, I. D.},

abstractNote = {Stochastic magnetization dynamics in uniformly magnetized nanomagnets is considered. The system is assumed to have rotational symmetry as the anisotropy axis, the applied field, and the spin polarization are all aligned along an axis of symmetry. By appropriate integration of the Fokker-Planck equation associated to the problem, the stochastic differential equation governing the evolution of the angle between the magnetization orientation and the symmetry axis is derived. The drift terms present in this equation contain a noise-induced drift term, which, in combination with drift terms of deterministic origin, can be written as the derivative of an effective potential. Superparamagnetic-like transitions are studied in connections with the bifurcations of the effective potential as temperature and excitation conditions are varied.},

doi = {10.1063/1.4906961},

journal = {Journal of Applied Physics},

issn = {0021-8979},

number = 17,

volume = 117,

place = {United States},

year = {2015},

month = {5}

}