Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metamagnetism and Weak Ferromagnetism in Nickel (II) oxalate crystals   Microcrystals of orthorhombic nickel (II) oxalate dihydrate were synthesized
through a precipitation reaction of aqueous solutions of nickel chloride and
oxalic acid. Magnetic susceptibility exhibits a sharp peak at 3.3 K and a
broadrounded maximum near 43 K. We associated the lower maximum with a
metamagnetic transition that occurs when the magnetic field is about \geq 3.5
T. The maximum at 43 K is the typical of 1D antiferromagnets, whereas weak
ferromagnetism behavior was observed in the range of 3.3 to 43 K.

16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph