Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Density and $T_1$ of surface and bulk spins in diamond in high magnetic
  field gradients   We report on surface and bulk spin density measurements of diamond, using
ultra-sensitive magnetic force microscopy with magnetic field gradients up to
0.5 T/$\mu$m. At temperatures between 25 and 800 mK, we measure the shifts in
the resonance frequency and quality factor of a cantilever with a micromagnet
attached to it. A recently developed theoretical analysis allows us to extract
a surface spin density of 0.072 spins/nm$^2$ and a bulk spin density of 0.4 ppm
from this data. In addition, we find an increase of the $T_1$ time of the
surface spins in high magnetic field gradients due to the suppression of spin
diffusion. Our technique is applicable to a variety of samples other than
diamond, and could be of interest for several research fields where surface,
interface or impurity bulk spin densities are an important factor.

8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th