Abstract
The study of abrupt increases in magnetization with magnetic field known as metamagnetic transitions has opened a rich vein of new physics in itinerant electron systems, including the discovery of quantum critical end points with a marked propensity to develop new kinds of order. However, the electric analogue of the metamagnetic critical end point, a “metaelectric” critical end point, has been rarely studied. Multiferroic materials wherein magnetism and ferroelectricity are cross-coupled are ideal candidates for the exploration of this novel possibility using magnetic-field (
H
) as a tuning parameter. Herein, we report the discovery of a magnetic-field-induced metaelectric transition in multiferroic BiMn
2
O
5
, in which the electric polarization (
P
) switches polarity along with a concomitant Mn spin–flop transition at a critical magnetic field
H
c
. The simultaneous metaelectric and spin–flop transitions become sharper upon cooling but remain a continuous cross-over even down to 0.5 K. Near the
P
= 0 line realized at μ
0
H
c
≈ 18
T
below 20 K, the dielectric constant (ɛ) increases significantly over wide field and temperature (
T
) ranges. Furthermore, a characteristic power-law behavior is found in the
P
(
H
) and ɛ(
H
) curves at
T
= 0.66 K. These findings indicate that a magnetic-field-induced metaelectric critical end point is realized in BiMn
2
O
5
near zero temperature.