Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Voltage controlled core reversal of fixed magnetic skyrmions without a
  magnetic field   Using micromagnetic simulations we demonstrate core reversal of a fixed
magnetic skyrmion by modulating the perpendicular magnetic anisotropy of a
nanomagnet with an electric field. We can switch reversibly between two
skyrmion states and two ferromagnetic states, i.e. skyrmion states with the
magnetization of the core pointing down/up and periphery pointing up/down, and
ferromagnetic states with magnetization pointing up/down, by sequential
increase and decrease of the perpendicular magnetic anisotropy. The switching
between these states is explained by the fact that the spin texture
corresponding to each of these stable states minimizes the sum of the magnetic
anisotropy, demagnetization, Dzyaloshinskii-Moriya interaction (DMI) and
exchange energies. This could lead to the possibility of energy efficient
nanomagnetic memory and logic devices implemented with fixed skyrmions without
using a magnetic field and without moving skyrmions with a current.

16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
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The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn