Multiferroic Crankshaft in GdMn2O5

Electric control of magnetism and magnetic control of ferroelectricity can improve
energy efficiency of magnetic memory and data processing devices. The
magnetoelectric switching requires more than just a coupling between spin and
charge degrees of freedom and is hard to achieve. We show that the application
and subsequent removal of magnetic field along a particular “magic” angle reverses
the electric polarization of the multiferroic GdMn₂O₅, induced by an
antiferromagnetic spin ordering. The polarization reversal appears together with an
unusual 4-state hysteresis cycle, in which one half of all spins undergoes a
unidirectional full-circle rotation in increments of ∼90 degrees.
GdMn₂O₅ thus resembles a microscopy magnetic analogue to a crankshaft,
converting the back and forth variations of the magnetic field into a circular spin
motion. The resulting magnetoelectric switching is independent of the sign of the
magnetic field and does not require magnetoelectric cooling. It is found that the 4-
state hysteresis regime emerges as a topologically distinct region (around the
magic angle) between two more regular 2-state hysteresis regions at high or low
field angles.