Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superparamagnetic response of Fe-coated W tips in spin-polarized
  scanning tunneling microscopy   We performed spin-polarized scanning tunneling spectroscopy on
biatomic-layer-high Co nanoislands grown on Cu(111) in magnetic fields oriented
normal to the sample surface, with Fe-coated W tips. Increasing the temperature
from 10 to 30 K, we observe a reduced slope of the differential conductance
around zero field. A quantitative analysis of the field- and
temperature-dependent differential conductance data in the framework of
superparamagnetism as described by a Langevin function gives an excellent
description of the experimental results. The analysis suggests that a Fe
nano-apex at the W tip, which is composed of 220-300 Fe atoms, determines the
magnetic response of the tip.

27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys