Secondments

All MagnEFi Early Stage Researchers will spend time on secondment at a second host institute within the consortium.  Some of the originally planned secondments have been delayed due to the Covid19 pandemic, but once the secondments have been completed, a brief summary will be posted here.

ESR13 Gyan van der Jagt: Spin-Ion -> USAL
Duration: 1 week remotely + 3 weeks (29/11/2021 – 17/12/2021) (4 weeks total)
Main Goals: 1. Simulation of magnetic domain wall motion in samples with varying crystalline disorder profiles created with He+irradiation. 2. Simulation of magnetic domain wall motion in wires with modulated disorder from the edges.

Gyan performed micromagnetic simulations on the field driven motion of magnetic domain walls in samples with different crystalline microstructures using the Mumax3 program. Under the supervision of Prof. Luis López Días, he performed an extensive set of characterizations regarding the interplay between the dispersion of magnetic properties along crystalline grains and the size of the grains, and their effect on the domain wall velocity at large fields. This knowledge was then used to compare simulated domain wall motion in three different films with varying microscopic structures with experimental data. The experimental data on the domain wall velocity as well as the micromagnetic parameters was obtained at Spin-Ion Technologies. From the results of the first project, he was able to confirm that the observed experimental changes in domain wall velocity were indeed influenced by different microscopic structures.

Gyan also initiated a second set of simulations, regarding domain wall motion in magnetic wires with disorder coming from the edges, and its modulation by ion irradiations. The initial simulations serve as a jumping off point for future micromagnetic simulations when more experimental data becomes available.

ESR 7 Beatrice Bednarz: JGU -> UPSaclay
Duration: 1 week (01/11/2021 – 05/11/2021)
Main goal: Learn how the ionic gating setup works and check the size of the effect on three types of samples

Beatrice conducted her first secondment at the Université Paris-Saclay under the guidance of Liza Herrera Diez. With the help of ESR 2 Rohit Pachat she successfully learned how to gate samples with ionic liquids. She investigated three types of samples: a ferromagnetic sample, a synthetic antiferromagnet and a natural antiferromagnet. The goal was to check how large the influence of the gating on the anisotropy is for the three types of samples. For this purpose, she used the Kerr microscope and the anomalous Hall effect setup to measure the hysteresis loops and image the domain patterns of the samples. The ferromagnetic and synthetic antiferromagnet samples showed a very strong effect of the gating. The antiferromagnetic sample didn’t show an effect yet. These results will be used for further sample optimization. Follow-up experiments will take place in 2022.

ESR 11 – Sreeveni Mozhikunnath Das, Aalto University, Finland -> INRIM, Turin
Duration 4 weeks (Sep 25 – Oct 25, 2021)
Main goal: Learn and perform DFT calculations for theoretical understanding of iDMI and magnetic anisotropy.

ESR 11 Sreeveni Mozhikunnath Das completed her first secondment at INRIM Turin from Sep 25 to Oct 25, 2021. The ESR is currently optimizing MgO/CoFeB/Ta heterostructure for hosting stable skyrmions. Hence the use of first principle calculations of MgO/CoFeB/Ta heterostructure will provide a theoretical understanding of the dzyaloshinskii-moriya interaction (DMI) and perpendicular magnetic anisotropy (PMA) contribution by various interfaces. She learned the basics of density functional theory and performed basic simulations including the design of super cells, structural relaxation and optimization of relevant parameters using the FLEUR package. Following the secondment, she will continue with DFT calculations and will perform magnetic force theorem calculations with spin orbit coupling for the estimation of magnetic anisotropy and DMI. Furthermore, the simulation results will be compared with experimental observations. 

ESR12 Cristina Balan: Institut Néel, CNRS -> USAL
Duration: 3 weeks (20/09/2021 – 15/10/2021) + 1 week remotely
Main goalSimulation of magnetic Domain Wall (DW) dynamics in non-centrosymmetric multilayer thin films with perpendicular magnetic anisotropy (PMA). 

Description:
Cristina completed, under the supervision of Prof Luis Lopez-Diaz, her first secondment at the University of Salamanca to simulate the motion of chiral Néel DW driven by an out-of-plane  magnetic field  in thin films stabilized by Dzyaloshinskii-Moriya interaction (DMI) . 
Using mumax3 program, micromagnetic simulations were carried out to reproduce the DW velocities, previously measured experimentally from bubble expansion in continuous thin films, to study in particular the regime above the Walker field, where the velocity is maintained high, without breakdown, in systems with large DMI. The magnetic parameters  implemented in the calculation (Ms, Keff, D) were measured at the Institut Néel.  The simulations were realised initially in the case of a perfect system with no disorder or temperature; later, different sized grains were introduced with different anisotropy distributions values to study the effects on the velocity of the DWs in the low field regime. 
Using these simulation results as reference, Cristina will carry out micromagnetic simulations to reproduce the DW velocities  measured in a similar magnetic system, but obtained after a voltage gate was applied for several minutes on  micro capacitor– like devices. This set of simulations are more challenging to realise, as the magnetic parameters were locally modified with electric field and only few of them could be measured, but of much interest as they can give a better understanding of how  magnetic DWs  can be efficiently used  in future spintronic applications.

ESR 1 Subhajit Roy: UPSaclay ->USAL
Duration: 2 weeks (05/07/2021 – 15/07/2021)
Main goal: Simulation of strain induced magnetic Domain Wall (DW) motion in thin film heterostructures 

Description:
ESR1 Subhajit Roy conducted his first secondment at the University of Salamanca to model the magnetic Domain Wall (DW) movement in thin films under the presence of strain using Mumax3. Due to Covid-19 travel restrictions, the first part of the secondment took place virtually. Over the duration of the secondment Subhajit had access to the University of Salamanca cluster remotely to perform simulations and at that time several methods, including online meetings and emails, were used for communication and discussion. From this short online secondment Subhajit learnt how to perform Magnetic DW movement simulation using Mumax3. Moreover, he also successfully simulated Field driven and Strain driven Magnetic DW movement under the supervision of Prof Luis Lopez-Diaz. In summary, Subhajit studied the influence of strain on the magnetic domain wall motion using Mumax3. The results show that strain is a significant tool for efficient manipulation of domain walls and could be used in further spintronic devices and applications. 

ESR 2 Rohit Pachat: Université Paris-Saclay -> Institut Néel, CNRS
Duration: 2 weeks (05/07/2021 – 16/07/2021)
Main Goal: Domain wall velocity (in the flow regime) and Asymmetric bubble expansion

Description:
ESR 2 Rohit Pachat conducted his first secondment at Institut Néel, CNRS to obtain domain wall (DW) velocity and effective DMI field (HDMI) in W/CoFeB/HfO2 thin films using MOKE under the supervision of Dr. Stefania Pizzini. Rohit studied the effect of different annealing conditions on the DW velocity and HDMI and correlated them. In addition, he also studied the same properties after the application of Electric field. The results obtained show that the influence of annealing parameters on magnetic properties is significant and optimizing the parameters for tuning magnetic properties is of great importance.

ESR3 Adriano di Pietro: INRIM -> UPSaclay
Duration: 4 weeks (07/06/2021 – 07/07/2021) 
Main goal: Collaboration with ESR2 on electrical fields

During his visit in at C2N in Paris, Adriano investigated the effect of annealing conditions and electric field treatment on DMI strength and domain wall velocity in HfO2/CoFeB/W multi-layers fabricated by Rohit Pachat. The results obtained by MOKE measurements seem to suggest that both these parameters have huge effects on the the aforementioned physical quantities and the application of an electric field was confirmed to be an effective method for increasing the domain wall velocity in the creep regime. Different annealing processes also have an important impact on the magnetic properties of the samples they alter the structural properties of magnetic interfaces at a very deep level. Further theoretical studies have to be carried out in order to outline how the degree of crystallinity of these interfaces can alter the magnetic properties of the samples. 

The measurements were not conclusive in showing that the E-field has a decisive impact on the tenability of DMI in these samples: the changes in said physical quantity were present but not large. These measurements sparked the interest to discover the mechanism giving rise to this particular behavior and helped in creating a template for future ab-initio simulations back in Turin, as well as providing further need for the secondment of Rohit Pachat to carry out measurements on more specialized equipment in the Institut Nèel (Grenoble).

ESR 4 Jintao Shuai: Leeds ->USAL
Duration: 8 weeks (08/04 – 02/06/2021)
Main goal: Simulation of thin films under surface acoustic waves

Description:
ESR4 Jintao Shuai conducted his first secondment at the University of Salamanca to model the magnetic behaviour of the thin films under surface acoustic waves (SAWs) using Mumax3. Due to Covid-19 travel restrictions, the secondment took place virtually. Various methods, including online meetings and emails, were used during the secondment to ensure the quality of the secondment. Account access to the University of Salamanca cluster was created to guarantee Jintao access to the necessary resources to perform simulations. Jintao Shuai successfully simulated standing and travelling SAWs under the supervision of Prof Luis Lopez-Diaz and Dr Eduardo Martinez. Jintao studied the influence of the SAW properties on the domain wall motion. The results show that surface acoustic waves-assisted domain wall motion is promising for efficiently manipulating domain walls, which is also beneficial to understanding the physics behind the phenomenon.

ESR 14 Mandy Syskaki: Singulus ->JGU
Duration: 2 weeks (5-18/10/2020)
Main goal: To learn about X-ray reflectivity and SQUID magnetometry

Description:
Under the guidance of Professor Gerhard Jakob, I deposited multi-layered material stacks in the Singulus ROTARIS sputtering tool, so that I could investigate the thickness and roughness of the layers by X-ray reflectometry using the four circle Bruker D8 Discover thin film-diffractometer, a technique I was not familiar with before. For the fitting of the obtained data, I learned to use the relevant software, i.e. Gen-X and Leptos. This gave me new insight into how to determine and optimize the quality of the films by tuning deposition parameters, such as pressure and power.

The second goal of my secondment was to learn how to use the SQUID magnetometer, which will allow me to investigate the magnetic properties of material stacks at lower temperatures. The magnetic moment of the different systems was measured as a function of the applied field at different temperatures.  

ESR9 Pingzhi Li: TU/e -> Smart Photonics
Duration: 5 weeks (08/10/20-20/11/20)
Main goal: To explore photonics circuit integration of magnetic nanostructures for circuit guided all-optical switching

Description:
Pingzhi completed his first secondment as a visiting researcher at “Smart Photonics”, which is a world leading fab producing chips based on integrated photonic circuits based on InP platform. There he became acquainted with the R&D and production of the cutting-edge integrated photonic system. During his stay, he made efforts to seek opportunities to bring the spintronic material into the standard photonic circuitry from the company in the hopes of extending the functionalities of both the integrated photonics and state-of-the-art spintronics through stack and circuit design. With obtained expertise as well as the connection with the company’s management and research teams, he aims to do further research into hybrid integration of spintronics into photonics.