Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous organic magnetoresistance from competing
  carrier-spin-dependent interactions with localized electronic and nuclear
  spins   We describe a new regime for low-field magnetoresistance in organic
semiconductors, in which the spin-relaxing effects of localized nuclear spins
and electronic spins interfere. The regime is studied by the controlled
addition of localized electronic spins to a material that exhibits substantial
room-temperature magnetoresistance ($\sim 20$\%). Although initially the
magnetoresistance is suppressed by the doping, at intermediate doping there is
a regime where the magnetoresistance is insensitive to the doping level. For
much greater doping concentrations the magnetoresistance is fully suppressed.
The behavior is described within a theoretical model describing the effect of
carrier spin dynamics on the current.

34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics