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Features of magnetization reversal in a MRAM cell — I. In-plane anisotropy
Authors
	Ostrovskaya N.V.
	Skidanov V.A.
	Iusipova Iu.A.
Date of publication
	2016
Abstract
	Magnetization dynamics in a three-layered nanopillar Co/Cu/Co structure with one fixed and one free layer driven by external magnetic field and spin-polarized electric current was investigated using methods of the theory of bifurcations. Mathematical model is based on the Landau--Lifshits--Gilbert equation with the current term in the Slonczewski–Berger form. Orientation of applied magnetic field was considered to be parallel to the anisotropy axis. Physical model included the anisotropy field and the demagnetizing field. Because of small size of the structure, the space dependence of magnetization, as usually [1–3], was not taken into account. The resulting system of equations has the form of the nonlinear dynamical system with the polynomial right sides. The analysis of singularities of the dynamical system was performed that allows finding the values of applied field and current, for which the phase portrait of the dynamical system is topologically equivalent. The qualitative changes of the phase portraits associated with bifurcations of singular points were investigated. Mathematical simulation of magnetization dynamics for typical values of field and current was performed. The numerical experiments revealed the features of switching process in more detail. The intervals of complete switching of magnetization from parallel to anti-parallel configuration were determined. It was brought to light that there is a region of control parameters where complete switching does not take place, but the free layer can be switched to the one of two intermediate axis-symmetrical positions (incomplete switching). Furthermore, the intervals of the field and the current where switching is fully impossible were found analytically. So, the approach of qualitative theory of dynamical systems permitted to find new regimes of magnetization dynamics, such as incomplete and accidental switching.
Keywords
	MRAM, perpendicular anisotropy, magnetization, free layer, fixed layer, the Landau–Lifshits–Gilbert equation, magnetization reversal
Library reference
	Ostrovskaya N.V., Skidanov V.A., Iusipova Iu.A. Features of magnetization reversal in a MRAM cell — I. In-plane anisotropy // Problems of Perspective Micro- and Nanoelectronic Systems Development - 2016. Proceedings / edited by A. Stempkovsky, Moscow, IPPM RAS, 2016. Part 4. P. 199-206.
URL of paper
	http://www.mes-conference.ru/data/year2016/pdf/D037.pdf