Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strong enhancement of direct magnetoelectric effect in strained
  ferroelectric-ferromagnetic thin-film heterostructures   The direct magnetoelectric (ME) effect resulting from the polarization
changes induced in a ferroelectric film by the application of a magnetic field
to a ferromagnetic substrate is described using the nonlinear thermodynamic
theory. It is shown that the ME response strongly depends on the initial strain
state of the film. The ME polarization coefficient of the heterostructures
involving Terfenol-D substrates and compressively strained lead zirconate
titanate (PZT) films, which stabilize in the out-of-plane polarization state,
is found to be comparable to that of bulk PZT/Terfenol-D laminate composites.
At the same time, the ME voltage coefficient reaches a giant value of 50 V/(cm
Oe), which greatly exceeds the maximum observed static ME coefficients of bulk
composites. This remarkable feature is explained by a favorable combination of
considerable strain sensitivity of polarization and a low electric permittivity
in compressively strained PZT films. The theory also predicts a further
dramatic increase of ME coefficients at the strain-induced transitions between
different ferroelectric phases.

5
The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph