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@ARTICLE{Sodernik:893187,
author = {Soderžnik, Kristina Žagar and Rožman, Kristina Žužek
and Komelj, Matej and Kovács, András and Diehle, Patrick
and Denneulin, Thibaud and Savenko, Aleksei and Soderžnik,
Marko and Kobe, Spomenka and Dunin-Borkowski, Rafal E. and
Mayer, Joachim and Markoli, Boštjan and Šturm, Sašo},
title = {{M}icrostructural insights into the coercivity enhancement
of grain-boundary-diffusion-processed {T}b-treated
{N}d-{F}e-{B} sintered magnets beyond the core-shell
formation mechanism},
journal = {Journal of alloys and compounds},
volume = {864},
issn = {0925-8388},
address = {Lausanne},
publisher = {Elsevier},
reportid = {FZJ-2021-02611},
pages = {158915 -},
year = {2021},
abstract = {We propose a dominant core-shell formation mechanism for
grain-boundary-diffusion-processed (GBDP), Tb-treated,
Nd2Fe14B sintered magnets. A depth-sensitive analysis of
Tb-treated samples, relative to a non-GBDP Nd2Fe14B magnet,
showed a $30\%$ increase of the coercivity in the central
part of the magnet. A structure-chemistry-magnetic-property
analysis revealed the dominant GBDP mechanism. On the
surface of the Tb-treated magnet, the Tb is released from
the starting precursor following a cascade of chemical
reactions between the Tb oxide and the Nd and/or the
Nd-Fe-B. The released Tb diffuses along the grain
boundaries, forming a core-shell structure. The calculated
optimum concentration for a $30\%$ increase in the
coercivity was 50 ppm of Tb. Off-axis electron-holography
measurements were used to quantitatively map the
characteristic magnetic states of the samples, confirming a
different magnetic domain structure in the shell than in the
core. The magnetic induction in the core was found to be
$26\%$ higher than that of the shell, which has a lower
magnetic saturation due to the presence of Tb. The results
show that the measured increase in the coercivity is due to
a structural effect, and not the magnetic contribution of
the Tb. Our results pave the way towards
grain-boundary-engineering studies that can be used to
increase the coercivity of Nd-Fe-B magnets for e-mobility
and eco-power applications.},
cin = {ER-C-1},
ddc = {540},
cid = {I:(DE-Juel1)ER-C-1-20170209},
pnm = {535 - Materials Information Discovery (POF4-535) / ESTEEM3
- Enabling Science and Technology through European Electron
Microscopy (823717) / 3D MAGiC - Three-dimensional
magnetization textures: Discovery and control on the
nanoscale (856538) / DFG project 405553726 - TRR 270:
Hysterese-Design magnetischer Materialien für effiziente
Energieumwandlung (405553726)},
pid = {G:(DE-HGF)POF4-535 / G:(EU-Grant)823717 /
G:(EU-Grant)856538 / G:(GEPRIS)405553726},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000624942300102},
doi = {10.1016/j.jallcom.2021.158915},
url = {https://juser.fz-juelich.de/record/893187},
}