Scaling of Dzyaloshinskii-Moriya interaction with magnetization in Pt/Co(Fe)B/Ir multilayers

Magnetic multilayers with perpendicular anisotropy and an interfacial Dzyaloshinskii-Moriya interaction (DMI) contain chiral domain walls and skyrmions that are promising for applications. Here, we measure the temperature dependence of the DMI in Pt/CoFeB/Ir and Pt/CoB/Ir multilayers by means of static domain imaging. First, the temperature dependences of saturation magnetization (Ms), exchange stiffness (A), and intrinsic perpendicular anisotropy (Ku) are determined. Then the demagnetized domain pattern in each multilayer is imaged by wide-field Kerr microscopy in the temperature range 9–290 K, and the characteristic domain period at each temperature is determined. We calculate the DMI constant D from an analytical expression for the domain wall energy density that treats the multilayer as a uniform medium. Scaling laws for Ku and D with the magnetization are established from the experiments. While the scaling of Ku is consistent with Callen-Callen theory, we find that the scaling of D is like that of A predicted theoretically (∼1.8)

Phase coexistence and transitions between antiferromagnetic and ferromagnetic states in a synthetic antiferromagnet

In synthetic antiferromagnets (SAFs), antiferromagnetic (AFM) order and synthesis using conventional sputtering techniques is combined to produce systems that are advantageous for spintronics applications. Here we present the preparation and study of SAF multilayers possessing both perpendicular magnetic anisotropy and the Dzyaloshinskii-Moriya interaction. The multilayers have an antiferromagnetically aligned ground state but can be forced into a full ferromagnetic (FM) alignment by applying an out-of-plane field ∼100mT. We study the spin textures in these multilayers in their ground state as well as around the transition point between the AFM and FM states at fields ∼40 mT by imaging the spin textures using complementary methods: photoemission electron, magnetic force, and Lorentz transmission electron microscopies. The transformation into a FM state by field proceeds by a nucleation and growth process, where skyrmionic nuclei form and then broaden into regions containing a ferromagnetically aligned labyrinth pattern that eventually occupies the whole film. Remarkably, this process occurs without any significant change in the net magnetic moment of the multilayer. The mix of antiferromagnetically and ferromagnetically aligned regions on the micron scale in the middle of this transition is reminiscent of a first-order phase transition that exhibits phase coexistence. These results are important for guiding the design of spintronic devices whose operation is based on spin textures in perpendicularly magnetized SAFs

La mentira como una estrategia de cortesía verbal: estudio pragmalinguístico de la telenovela La Saga

Even though languages have many things in common they all differ in the way politeness is present in verbal interactions. What might be polite in certain cultures can be considered impolite in other cultures, and this is due to the relationships among the speaker and the hearer, their context, their social needs, desires, and expectations. In this thesis I will try to provide a contextual explanation for some Colombians\u27 use of lies (as a means of politeness to deceive) in their daily life through conversations based on some of Colombia\u27s history. Lies have become so internalized by many Colombian people in their language that they even feel weird if they tell the truth. This is reflected in the soap opera La Saga, which was very well accepted among the TV viewers due in part to its realistic depiction of reality in Colombian society. The selected conversations will be analyzed taking into account the politeness theory and the concept of face proposed by Brown and Levinson. I will also analyze the maxims and the cooperative principle proposed by Grice. These philosophers of language, along with Haverkate, analyzed language based on the idea that we do actions with words. I selected thirteen conversations from the soap opera La Saga, which show the interlocutors lying. My idea is to identify if a speaker is using lies, as a politeness strategy to deceive the hearer. As a result I found that some Colombian people use lies frequently; some lies are more socially- accepted than others and those lies can become acceptable when they satisfy social conventions. Most of the lies found in the recorded conversations were used as a politeness strategy when the speaker intended to deceive the hearer (for whatever reason), which led me to conclude that the desire to protect the speaker\u27s face is stronger than his/her desire to protect the hearer\u27s, either to avoid confrontations, discrepancies, uncomfortable situations or unpleasant interactions

Dataset Associated with Breathing Modes of Skyrmion Strings in a Synthetic Antiferromagnet

Dataset associated with publication on skyrmion breathing modes in a synthetic ntiferromagnetic multilayer. All data was generated using the micromagnetic solver mumax3, studying the static behaviour of skyrmions as a function of applied magnetic field, and interlayer antiferromagnetic coupling strength. Also studied are the breathing modes of these skyrmions as a function of field, coupling strength structural disorder and temperature

Domain wall motion at low current density in a synthetic antiferromagnet nanowire

Dataset associated with publication on SAF domain wall motion. Dataset contains data on magnetisation vs field and magnetisation vs temperature collected on a quantum design SQUID VSM, and data collected on the PolLux endstation of the Swiss Lightsource, containing a mix of full XMCD images of domain walls in a SAF microwire, and single STXM images where the domain wall motion is calculated from the difference between each subsequent image

Deviations from bulk behavior in TbFe(Co) thin films: Interfaces contribution in the biased composition

International audienceFerrimagnetic TbFe or TbFeCo amorphous alloy thin films have been grown by coevaporation in ultrahigh vacuum. They exhibit an out-of-plane magnetic anisotropy up to their Curie temperature with a nucleation and propagation reversal mechanism suitable for current induced domain wall motion. Rutherford backscattering experiments confirmed a fine control of the Tb depth-integrated composition within the evaporation process. However, a large set of experimental techniques were used to evidence an interface related contribution in such thin films as compared to much thicker samples. In particular, scanning transmission electron microscopy experiments evidence a depth dependent composition and perturbed top and bottom interfaces with preferential oxidation and diffusion of terbium. Despite that, amorphous and homogeneous alloy film remains in a bulklike part. The composition of that bulklike part of the magnetic layer, labeled as effective composition, is biased when compared with the depth-integrated composition. The magnetic properties of the film are mostly dictated by this effective composition, which we show changes with different top and bottom interfaces