Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NMR as a probe of the relaxation of the magnetization in magnetic
  molecules   We investigate the time autocorrelation of the molecular magnetization $M(t)$
for three classes of magnetic molecules (antiferromagnetic rings, grids and
nanomagnets), in contact with the phonon heat bath. For all three classes, we
find that the exponential decay of the fluctuations of $M(t)$, associated with
the irreversible exchange of energy with the heat bath, is characterized by a
single characteristic time $\tau (T,B)$ for not too high temperature $T$ and
field $B$. This is reflected in a nearly single-lorentzian shape of the
spectral density of the fluctuations. We show that such fluctuations are
effectively probed by NMR, and that our theory explains the recent
phenomenological observation by Baek et al. (PRB70, 134434) that the
Larmor-frequency dependence of $1/T_1$ data in a large number of AFM rings fits
to a single-lorentzian form.

29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an