My work

I recently had the honour of giving an invited talk on Heat-assisted Magnetic Recording (HAMR) at the Ex-Spring Industrial Conclave which was hosted by Exeter University. Apart from introducing the magnetic recording paradigms (LMR, PMR and HAMR) and emphasizing the need for energy-assisted magnetic recording in order to continue areal density growth, I shared details on the HAMR recording physics and highlighted challenges that have been overcome in the last few years in order to bring HAMR to product....

UPDATE: These days it is recommended to use Python3 instead of Python2 Apparently it is tricky to get Python integration working in the KNIME Analytics Platform. If you read the official guide too quickly you can miss some critical information at the bottom of the page. I was getting an error complaining that the google.protobuf library was missing even though I thought that I had everything installed correctly: Library google.protobuf is missing, required minimum version is 2....

Our latest paper has just been published in the journal Acta Materialia. In it, we compare finite element micromagnetics simulations to experimental evidence in order to investigate the role of twin and anti-phase defects in the reduction of performance in MnAl permanent magnets. Figure: Room temperature (BH) max as a function of approximate raw material costs for the theoretical MnAl permanent magnet and experimental values for a selection of common commercial permanent magnets....

The problem of how to visualize multivariate data sets is something I often face in my work. When using numerical optimization we might have a single objective function and multiple design variables that can be represented by columnar data in the form {x1, x2, x3, … xn, y} a.k.a. NXY. With design spaces of more than a few dimensions it is difficult to visualize them in order to estimate the relationship between each independent variable and the objective, or perform a sensitivity study....

New paper The reprint of our Journal of Applied Physics (JAP) paper “Grain-size dependent demagnetizing factors in permanent magnets” has been updated since the old version was not being discovered by the Google Scholar crawler. There is also now a version on arXiv. I hope that Google Scholar will now correctly index the paper so that it’s easier for people to find! Citation The full, correct reference for the paper is:...

New paper Our latest paper has been published in JOM (Springer). It is a summary of the achievements (so far) of the ROMEO fp7 project. ROMEO is a project that aims to research and develop novel microstructural-engineering strategies that will dramatically improve the properties of magnets based purely on light rare earth elements, especially the coercivity, which will enable them to be used for applications above 100 degrees C. Abstract The rare-earth crisis, which peaked in the summer of 2011 with the prices of both light and heavy rare earths soaring to unprecedented levels, brought about the widespread realization that the long-term availability and price stability of rare earths could not be guaranteed....

This week our new paper titled “Thermal Activation in Permanent Magnets” has been published in JOM (Springer). The invited paper is under a special topic, “Permanent Magnets beyond Nd-Dy-Fe-B”. An author manuscript (reprint) is available here. Fig 1: Explanation of method for calculating the thermally activated coercivity of using micromagnetics. In the paper we provide a more detailed overview of the micromagnetic methods we have developed to model the thermal activation of permanent magnets....

Our EU-funded FP7 project “Replacement and Original Magnet Engineering Options” (ROMEO) has recently been covered in the news in Slovenia, to promote the participation of our Slovenian collaborators. Video »Video file« Newsletter There is also now a project newsletter highlighting the aims and progress of the project. Please click here to download it.

Our new paper “Thermally activated coercivity in core-shell permanent magnets” has been published today as J. Appl. Phys. 117, 17A733 (2015); http://dx.doi.org/10.1063/1.4916542 . In the paper we use numerical miromagnetics to calculate the performance of nanostructured core-shell-like permanent magnets, like the type that can now be produced by grain boundary diffusion of granular hot-deformed or sintered rare earth permanent magnets. FIG. 3. Reversal processes in the sin- gle grain models with (i) a pure NdFeB grain, (ii) a NdFeB grain with a soft outer defect, and (iii) NdFeB core, (Dy, Nd)FeB shell and an outer soft defect....

Our paper titled “Micromagnetics for the coercivity of nanocomposite permanent magnets” has been published in the proceedings of the 23rd International Workshop on Rare Earth and Future Permanent Magnets and Their Applications (REPM2014). The proceedings were not made available to the public but we are providing a PDF reprint here. Fig. 1. Switching field of Nd 2 Fe 14 B cubes and spheres with volume V The work was presented by Johann Fischbacher on 19th August 2014 in Annapolis, Maryland....

Our paper titled “Enhanced Nucleation Fields due to Dipolar Interactions in Nanocomposite Magnets” was presented by first author, Johann Fischbacher, at the JEMS 2012 conference and subsequently published in the The European Physical Journal B. Figure: Magnetic reversal process: The pictures show the magnetic flux lines. The color denotes the magnetization direction (red: magnetization up, blue magnetization down). The gap between the soft magnetic spheres (d incl = 8 nm) is 1 nm in the first two columns and 4 nm in the third column....