Study on the coherence degree of magnetization reversal in Permalloy single-domain nano-ellipses

• Published in: Journal of magnetism and magnetic materials Vol. 426; pp. 396 - 404
• Main Authors: Júnior, D.S. Vieira, Leonel, S.A., Toscano, D., Sato, F., Coura, P.Z., Dias, R.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.03.2017; Elsevier BV
• Subjects: Coherence; Coherent rotation; Computer simulation; Ellipses; Ferrous alloys; Geometry; Magnetic fields; Magnetization dynamics; Magnetization reversal; Nanomaterials; Single-domain nano-elements; Magnetization reversal; Single-domain nano-elements; Magnetization dynamics; Coherent rotation
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2016.11.097

Numerical simulations have been performed to study the magnetization reversal in Permalloy nano-ellipses, under combined in-plane magnetic fields along the longitudinal and the transverse directions. We have considered nano-ellipses with two different aspect ratios and five thicknesses: 220×80×tnm3 and 70×50×tnm3, where t ranging from 5 to 25nm in steps of 5nm. We found that the mechanism of magnetization reversal is not only dependent on the parameters of the magnetic field pulse but also related to the ellipse dimensions. It is known that the reversal time is related to the mechanism behind the magnetization reversal. In particular, ultrafast magnetization reversals occur by coherent rotation, when applying a field oriented mainly perpendicular to the initial magnetization. In order to evaluate the degree of coherence of the magnetization reversal we have introduced a quantity called “coherence index”. Besides complementing the previous studies by including the effect of the thickness on the magnetization reversal, our results indicate that it is possible to obtain magnetization reversals with high degree of coherence in small nano-ellipses by adjusting the geometric factors of the ellipse and the parameters of the magnetic field pulse simultaneously. •Magnetization reversals in single-domain nano-ellipses were investigated.•A parameter to evaluate the degree of coherence of the magnetization reversal was proposed.•A higher coherence index indicates a complete, coherent, rotation of the magnetization.