Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: From soft to hard magnetic Fe-Co-B by spontaneous strain: A combined
  first principle and thin film study   In order to convert the well-known Fe-Co-B alloy from a soft to a hard
magnet, we propose tetragonal strain by interstitial boron. Density functional
theory reveals that when B atoms occupy octahedral interstitial sites, the bcc
Fe-Co lattice is strained spontaneously. Such highly distorted Fe-Co is
predicted to reach a strong magnetocrystalline anisotropy which may compete
with shape anisotropy. Probing this theoretical suggestion experimentally,
epitaxial films are examined. A spontaneous strain up to 5 % lattice distortion
is obtained for B contents up to 4 at%, which leads to uniaxial anisotropy
constants exceeding 0.5 MJ/m^3. However, a further addition of B results in a
partial amorphization, which degrades both anisotropy and magnetization.

23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
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
28
The categories of this paper are: alg-geom