Periodic Reporting for period 3 - NOVAMAG (NOVel, critical materials free, high Anisotropy phases for permanent MAGnets, by design.)
Reporting period: 2018-10-01 to 2019-09-30
The magnetic properties of the newly predicted phases and of known optimized phases identified in WP1 were studied by first principles methods. These magnetic properties comprise: magnetic moments, MAE, exchange coupling constants, Curie temperature, M(T), thermodynamics. Calculated magnetic properties of the new phases and known optimized phases, together with experimental data, are being included in a very comprehensive database that will be ready at the end of the project. We follow the European Material Modelling Ontology (EMMO) and construct the database taxonomy and ontology based on MODA.
A very wide and comprehensive experimental screening of the predicted phases has been carried out by several techniques: combinatorial sputtering, reactive crucible melting and non-equilibrium techniques, such as melt spinning or mechanical alloying. Among all the samples that were produced, some were already discarded. Some compounds, with very promising properties, have not been produced so far, but further efforts will be done.
The influence of the microstructure and temperature on the coercivity and maximum energy product were theoretically studied. Interface properties and grain boundary stability were studied by means of density functional theory (DFT) calculations and molecular dynamics simulations. Promising candidate phases for rare-earth free permanent magnets were studied with respect to interfaces and grain boundaries. In addition, spin dynamics simulations were used to compute the temperature dependence of the intrinsic magnetic properties and to calculate the influence of local anisotropy variations next to interfaces on coercivity.
The microstructure of a magnet is essential for developing coercivity. The influence of the microstructure on coercivity, remanence, and energy density product was studied using micromagnetic simulations. In these simulations synthetic microstructures were built and discretized with finite elements. Using numerical optimization tools, the structures were optimized, in order to maximize the coercive field or the energy density product. Structure optimization was performed for possible candidate phases. A study on the influence of thermal activation on the coercive field of permanent magnets made from candidate phases was also carried out.
A full structural, thermodynamic and magnetic characterization has been carried out in samples produced in WP3. Different characterization techniques provide information complementary to each other. The experimental results are compared with the predictions obtained by theoretical groups, so that they can adjust the models and computing methods with our input, to get a better understanding of the real behavior, and improve further predictions.
TUDA performed systematic calculations on FeNi+X and FeCo+X (X=H, B, C and N) to study the induced tetragonal distortion. It has been observed that N tends to stabilize an enhanced tetragonal distortion of the FeNi lattice. Experimentally, NCRSD was able to obtain an important percentage of the tetragonal phase in bulk by flux melting with In. Actually, this important finding could be subject for a patent application, as industrial partners pointed in WP9. We expect to obtain an even larger percentage of the tetragonal phase by optimization of the synthesis techniques.
In the following months, we expect to produce bonded (Nd-based nitrogenated 1:12 alloys) and sintered magnets (Sm-based 1:12 alloys) and also by additive manufacturing (Mn-Al-C alloys). The magnetic properties of these magnets will be measured and we expect to obtain results that would be interesting for industries to produce and use our magnets. If successful results are obtained for these magnets we would have achieved a large reduction of the RE-content in PM and so CRM-content.
The database that we are currently designing and implementing would comprise very useful information for both theoreticians and experimentalists about not only structural but also magnetic properties of a very wide range of compounds. This database will be open for users so everyone can access and take advantage of our research.