Local Thermoelectric Response from a Single Néel Domain Wall

Spatially resolved thermoelectric detection of magnetic systems provides a unique platform for the investigation of spintronic and spin caloritronic effects. Hitherto, these investigations have been resolution limited, confining analysis of the thermoelectric response to regions where the magnetisation is uniform or collinear at length scales comparable to the domain size. Here, we investigate the thermoelectric response from a single trapped domain wall using a heated scanning probe. Following this approach, we unambiguously resolve the domain wall due to its local thermoelectric response. Combining analytical and thermal micromagnetic modelling, we conclude that the measured thermoelectric signature is unique to that of a domain wall with Néel like character. Our approach is highly sensitive to the plane of domain wall rotation, which permits the distinct identification of Bloch or Néel walls at the nanoscale and could pave the way for the identification and characterisation of a range of non-collinear spin textures through their thermoelectric signatures

Thermoelectric signature of individual skyrmions

We experimentally study the thermoelectrical signature of individual skyrmions in chiral Pt/Co/Ru multilayers. Using a combination of controlled nucleation, single skyrmion annihilation, and magnetic field dependent measurements the thermoelectric signature of individual skyrmions is characterized. The observed signature is explained by the anomalous Nernst effect of the skyrmions spin structure. Possible topological contributions to the observed thermoelectrical signature are discussed. Such thermoelectrical characterization allows for non-invasive detection and counting of skyrmions and enables fundamental studies of topological thermoelectric effects on the nano scal

Radially dependent stray field signature of chiral magnetic skyrmions

Magnetic skyrmions are topological spin structures that arise in chiral magnetic systems which exhibit broken inversion symmetry and high spin-orbit coupling resulting in a sizable Dzyaloshinskii-Moriya interaction. Understanding the local spin texture of skyrmions is a vital metrological step in the development of skyrmionic technologies required for novel logic or storage devices in addition to providing fundamental insight into the nanoscale chiral interactions inherent to these systems. Here, we propose that there exists a radially dependent stray field signature that emanates from magnetic skyrmions. We employ quantitative magnetic force microscopy to experimentally explore this stray field signature. To corroborate the experimental observations a semianalytical model is developed which is validated against micromagnetic simulations. This unique approach provides a route to understand the unique radially dependent field signature from skyrmions, which allows an understanding of the underlying local magnetization profile to be obtained. From a practical standpoint, our results provide a rapid approach to validate outputs from numerical or micromagnetic simulations. This approach could be employed to optimize the complex matrix of magnetic parameters required for fabricating and modeling skyrmionic systems, in turn accelerating the technology readiness level of skyrmionic based devices

A Ti/Pt/Co Multilayer Stack for Transfer Function Based Magnetic Force Microscopy Calibrations

Magnetic force microscopy (MFM) is a widespread technique for imaging magnetic structures with a resolution of some 10 nanometers. MFM can be calibrated to obtain quantitative (qMFM) spatially resolved magnetization data in units of A/m by determining the calibrated point spread function of the instrument, its instrument calibration function (ICF), from a measurement of a well-known reference sample. Beyond quantifying the MFM data, a deconvolution of the MFM image data with the ICF also corrects the smearing caused by the finite width of the MFM tip stray field distribution. However, the quality of the calibration depends critically on the calculability of the magnetization distribution of the reference sample. Here, we discuss a Ti/Pt/Co multilayer stack that shows a stripe domain pattern as a suitable reference material. A precise control of the fabrication process, combined with a characterization of the sample micromagnetic parameters, allows reliable calculation of the sample’s magnetic stray field, proven by a very good agreement between micromagnetic simulations and qMFM measurements. A calibrated qMFM measurement using the Ti/Pt/Co stack as a reference sample is shown and validated, and the application area for quantitative MFM measurements calibrated with the Ti/Pt/Co stack is discussed