Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Relevance of $4f$-$3d$ exchange to finite-temperature magnetism of
  rare-earth permanent magnets: an ab-initio-based spin model approach for
  NdFe$_{12}$N   A classical spin model derived ab initio for rare-earth-based permanent
magnet compounds is presented. Our target compound, NdFe$_{12}$N, is a material
that goes beyond today's champion magnet compound Nd$_{2}$Fe$_{14}$B in its
intrinsic magnetic properties with a simpler crystal structure. Calculated
temperature dependence of the magnetization and the anisotropy field agree with
the latest experimental results in the leading order. Having put the realistic
observables under our numerical control, we propose that engineering
$5d$-electron-mediated indirect exchange coupling between $4f$-electrons in Nd
and $3d$-electrons from Fe would most critically help to enhance the material's
utility over the operation-temperature range.

17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th