Room-temperature sodium–sulfur batteries are promising battery systems because of their high theoretical capacity, high energy density, and low cost. However, their application is hindered by several issues, especially linked with the polysulfide shuttle effect. Herein, Al2O3–Nafion membrane is used to prevent migration of polysulfides from the cathode side to the anode assisting to lessen the active material loss. While Al2O3 is a very effective adsorbent to trap polysulfides anions, Nafion membrane has cation selectivity which permits migration of Na+ cations and repels polysulfide anions due to the negatively charged sulfonic groups. Thus, an increase in the performance of room-temperature sodium–sulfur batteries (RT Na–S batteries) is expected by combining their constructive effects. As a result, higher capacity retention is achieved with ∼250 mAh/g capacities after 100 cycles in the presence of Al2O3–Nafion membrane in contrast to the cell without any interlayer.

We report the quantum calibration of a magnetic force microscope (MFM) by measuring the two-dimensional magnetic stray field distribution of the tip MFM using a single nitrogen vacancy (NV) center in diamond. From the measured stray field distribution and the mechanical properties of the cantilever a calibration function is derived allowing to convert MFM images in quantum calibrated stray field maps. This novel approach overcomes limitations of prior MFM calibration schemes and allows quantum calibrated nanoscale stray field measurements in a field range inaccessible by scanning NV magnetometry. Quantum calibrated measurements of a stray field reference sample allow its use as a transfer standard opening the road towards fast and easily accessible quantum traceable calibration of virtually any MFM.

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.