Aleš Hrabec's Thesis Defense: "Study of the magnetization dynamics in nanostructures with perpendicular anisotropy: effect of magnetic field and electric current"
Tuesday 6 Decembre 2011 at 2pm
Lecture Room - 1st floor -Building A
CNRS Polygone scientifique
25 rue des martyrs, 38000 Grenoble
Aleš HRABEC (Institut Néel)
Thesis supervisors: Stéfania PIZZINI & Laurent RANNO
Within the last two decades, the domain wall manipulation became one of the undetachable parts of spintronics. The interaction between spin-polarized conduction electrons and localized magnetic moments in terms of giant magnetoresistance in 1988 and in terms of spin-transfer torque in 1996, launched an avalanche of experimental work on current-induced magnetization dynamics. Despite the very intensive research in this field, many fundamental questions stay unanswered. For example, the origin of the phenomenological parameters alpha and beta, being at the heart of the description of the magnetization dynamics, is not fully understood. Usually, in the experimentally studied systems the micromagnetic parameters are fixed, so that it is impossible to verify their role in magnetization dynamics. Tuning of such parameters like magnetization or angular momentum, domain wall width, etc., would shed more light on the understanding of the field- or current-induced domain wall dynamics process. In the first part of my work I will describe an alloy of Gd(1-x)Co(x) with an induced composition, i.e. magnetization, gradient. The alloy composition is chosen in the way that a magnetically compensated interface is present in our thin films. Such a thin film serves as an ideal model system with a continuous change of magnetization at a constant temperature. This system is the subject of a study of field- current- and light-induced magnetization dynamics. In the second part of the work, PtCoAlOx trilayer, a system already shown to be suitable for fast and reproducible domain wall manipulation is studied. I experimentally tested and prove the hypothesis connecting the spin-transfer torque efficiency with a transverse magnetic field having as origin the Rashba field at the Co interfaces.
Keywords: ferrimagnetic materials, magnetic films, domain walls, magnetization reversal