Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin current in the Kondo lattice model   By using the projection operator technique it is observed that the strong
Hund's rule coupling and s-d interaction in transition metal elements may lead
to an effective coupling between the spin current and spin spirality. As a
result, the spin spirality can be regarded as a driving force to produce a spin
current. The spin current may give rise to a novel type of field acting on the
spins. A spin battery is designed based on the interactions between the spin
current and spin spirality.

10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org