Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic and superconducting phase diagram of
  Eu(Fe$_{1-x}$Ni$_{x}$)As$_{2}$   We report the Ni-doping effect on magnetism and superconductivity (SC) in an
Eu-containing 112-type system Eu(Fe$_{1-x}$Ni$_{x})$As$_{2}$ ($0\leq x\leq
0.15$) by the measurements of resistivity, magnetization, and specific heat.
The undoped EuFeAs$_2$ undergoes a spin-density-wave (SDW) transition at
$T_\mathrm{SDW}\sim$ 105 K in the Fe sublattice and a magnetic ordering at
$T_\mathrm{m}\sim$ 40 K in the Eu sublattice. Complex Eu-spin magnetism is
manifested by a spin-glass reentrance at $T_\mathrm{SG}\sim$ 15 K and an
additional spin reorientation at $T_\mathrm{SR}\sim$ 7 K. With Ni doping, the
SDW order is rapidly suppressed, and SC emerges in the Ni-doping range of 0.01
$\leq x\leq$ 0.1 where a maximum of the superconducting transition temperature
$T_\mathrm{c}^{\mathrm{max}}=$ 17.6 K shows up at $x$ = 0.04. On the other
hand, $T_\mathrm{m}$ decreases very slowly, yet $T_\mathrm{SG}$ and
$T_\mathrm{SR}$ hardly change with the Ni doping. The phase diagram has been
established, which suggests a very weak coupling between SC and Eu spins. The
complex Eu-spin magnetism is discussed in terms of the
Ruderman-Kittel-Kasuya-Yosida interactions mediated by the conduction electrons
from both layers of FeAs and As surrounding Eu$^{2+}$ ions.

33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc