Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $^{77}$Se NMR evidence for the Jaccarino-Peter mechanism in the field
  induced superconductor, $\lambda$(BETS)$_2$FeCl$_4$}   We have performed $^{77}$Se NMR on a single crystal sample of the field
induced superconductor $\lambda$-(BETS)$_{2}$FeCl$_{4}$. Our results obtained
in the paramagnetic state provide a microscopic insight on the exchange
interaction $J$ between the spins \textbf{s} of the BETS $\pi$ conduction
electrons and the Fe localized $d$ spins \textbf{S}. The absolute value of the
Knight shift \textbf{K} decreases when the polarization of the Fe spins
increases. This reflects the ``negative'' spin polarization of the $\pi$
electrons through the exchange interaction $J$. The value of $J$ has been
estimated from the temperature and the magnetic field dependence of \textbf{K}
and found in good agreement with that deduced from transport measurements (L.
Balicas \textit{et al}. Phys. Rev. Lett. \textbf{87}, 067002 (2001)). This
provides a direct microscopic evidence that the field induced superconductivity
is due to the compensation effect predicted by Jaccarino and Peter (Phys. Rev.
Lett. \textbf{9}, 290 (1962)). Furthermore, an anomalous broadening of the NMR
line has been observed at low temperature, which suggests the existence of
charge disproportionation in the metallic state neighboring the superconducting
phase.

26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph