Magnetostriction-polarization coupling in multiferroic Mn2MnWO6

Abstract

Double corundum-related polar magnets are promising materials for multiferroic and magnetoelectric applications in spintronics. However, their design and synthesis is a challenge, and magnetoelectric coupling has only been observed in Ni₃TeO₆ among the known double corundum compounds to date. Here we address the high-pressure synthesis of a new polar and antiferromagnetic corundum derivative Mn₂MnWO₆, which adopts the Ni₃TeO₆-type structure with low temperature first-order field-induced metamagnetic phase transitions (T _N = 58 K) and high spontaneous polarization (~ 63.3 μC·cm^-2). The magnetostriction-polarization coupling in Mn₂MnWO₆ is evidenced by second harmonic generation effect, and corroborated by magnetic-field-dependent pyroresponse behavior, which together with the magnetic-field-dependent polarization and dielectric measurements, qualitatively indicate magnetoelectric coupling. Piezoresponse force microscopy imaging and spectroscopy studies on Mn₂MnWO₆ show switchable polarization, which motivates further exploration on magnetoelectric effect in single crystal/thin film specimens.

Fig. 1

Crystal structure of Mn₂MnWO₆. The three-dimensional framework structure of Mn₂MnWO₆ viewed along [110] direction, to show the face-sharing Mn1O₆-WO₆ and Mn2O₆-Mn3O₆ octahedral pairs along the c-axis and the edge-sharing Mn1O₆-Mn3O₆ and Mn2O₆-WO₆ octahedral pairs in the ab-plane. The color codes of spheres are corresponding to Mn1-green, Mn2-purple, Mn3-cyan; W-light gray, O1-red, and O2-orange

Fig. 2

Magnetic properties of Mn₂MnWO₆. a Thermal evolution of the ZFC and FC mode magnetization (M) and the reciprocal susceptibility (inset) of Mn₂MnWO₆ measured with H = 0.1 T up to 400 K. b A logarithmic plot of the M(T) curves at a series of magnetic fields between 0.005 and 14 T. The dashed line highlights the evolution of AFM transition temperatures. The dash-dot line highlights the presence of local magnetic correlations near 60 K in all finite magnetic fields. c Isothermal magnetization curves of Mn₂MnWO₆ measured at 2, 20, 50, 100, and 300 K between -14 and 14 T for 2 and 20 K; -7 and 7 T for 50, 100, and 300 K. Inset shows the curves between -3 and 3 T

Fig. 3

Illustration of the nuclear and magnetic structures of Mn₂MnWO₆ at 5 K. Mn1, Mn2, Mn3 and W sites and polyhedra are shown in green, purple, blue and grey, respectively, with Mn moments shown by red arrows (color online) (oxide ions are omitted for clarity). a shows the complete magnetic structure (showing six times the nuclear unit cell along c). b shows only the z component of Mn moments (described by commensurate mT1 irrep) and c shows only the xy component of Mn1 and Mn3 moments (described by mΛ2LE2 irrep) (showing six times the nuclear unit cell along c), also d showing view down along c axis of magnetic unit cell

Fig. 4

Magnetostriction-polarization coupling and pyroresponse in Mn₂MnWO₆. a Temperature dependent spontaneous polarization (P _S, calculated) and Mn2-Mn3 distance evolution in Mn₂MnWO₆ between 5 and 100 K. b Pyro-current as a function of temperature between 10 and 80 K, and c Pyroelectric polarization measured in 0 and 1 T upon warming and normalized to a common high temperature value. d Temperature dependent dielectric data between 0 and 10 T show anomalies around T _N and indicate magnetoelectric coupling

Fig. 5

PFM results on Mn₂MnWO₆. a Topography (scale bar 250 nm). b PFM DART amplitude and c phase. d average amplitude (i) and phase (ii) BE PFM switching spectroscopy loops determined from square regions indicated in the phase image in (c). Remnant e negative and f positive amplitudes determined from fitting 35 × 35 grid measurement. Scale bar is the same for Fig. 5a–c