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In this work, we use laser powder bed fusion (LPBF) to produce Nd-Fe-B magnets. A suitable process window is developed, which allows to fabricate isotropic samples with outstanding magnetic performance. The sample quality is mainly defined by the energy input during LPBF and sintering or delamination occurs, if the process parameter are improperly adjusted. Magnetic and structural properties become better as energy input increases, until the material-specific limit for processability has been reached. Magnets with coercivity of 886 kA/m (µ 0 H c = 1.1 T) and maximum energy product of 63 kJ/m 3 can be produced from Nd-lean commercial powder without any post treatment. Thereby, our samples represent the new benchmark for permanent magnets produced by additive manufacturing. On the example of coercivity, the impact of laser power, scan velocity and hatch spacing is discussed. It is shown that coercivity can be sufficiently well described by a simple phenomenological model.

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A hot-deformed Nd-Fe-B sample has been chosen for the investigation of interaction domains by means of magnetic force microscopy. During the imaging process, a magnetic field of up to 6 T was applied in situ along the easy axis of magnetization. The thermally demagnetized state presents a regular pattern of interaction domains with an average width of about 1 μm but with a much larger length scale. Starting from the thermally demagnetized state, magnetization along the initial magnetization curve occurs via sequential switching of neighboring grain columns at the peripheries of the interaction domains. Demagnetization of a saturated sample takes place through the nucleation and expansion of a patchy domain pattern with a much larger extension and a substructure in the lateral range of the underlying grain size. Reversal processes under an applied magnetic field also take place at the borders of the domains.

Demagnetization curves of sub-micron Nd 2 Fe 14 B particles with rectangular prism shapes were simulated by micromagnetic simulations. Coercivity decreases with increasing particle thickness for same particle volumes. This unexpected behavior can be explained by different resulting angles of the total effective field when superimposing the applied field vector with the stray field vector at the point of the first reversal event. The angular dependence of the nucleation field follows a Stoner-Wohlfarth like behavior. V