  The notion of a simple ordered state implies homogeneity. If the order is
established by a broken symmetry, elementary Landau theory of phase transitions
shows that only one symmetry mode describes this state. Precisely at points of
phase coexistence domain states formed of large regions of different phases can
be stabilized by long range interactions. In uniaxial antiferromagnets the
so-called metamagnetism is an example of such a behavior, when an
antiferromagnetic and field-induced spin-polarized paramagnetic/ferromagnetic
state co-exist at a jump-like transition in the magnetic phase diagram. Here,
combining experiment with theoretical analysis, we show that a different type
of mixed state between antiferromagnetism and ferromagnetism can be created in
certain acentric materials. In the small-angle neutron scattering experiments
we observe a field-driven spin-state in the layered antiferromagnet Ca3Ru2O7,
which is modulated on a scale between 8 and 20 nm and has both
antiferromagnetic and ferromagnetic parts. We call this state a metamagnetic
texture and explain its appearance by the chiral twisting effects of the
asymmetric Dzyaloshinskii-Moriya (DM) exchange. The observation can be
understood as an extraordinary coexistence, in one thermodynamic state, of spin
orders belonging to different symmetries. Experimentally, the complex nature of
this metamagnetic state is demonstrated by measurements of anomalies in
electronic transport which reflect the spin-polarization in the metamagnetic
texture, determination of the magnetic orbital moments, which supports the
existence of strong spin-orbit effects, a pre-requisite for the mechanism of
twisted magnetic states in this material.
