Magnetic and orbital correlations in multiferroic CaMn${}_7$O${}_{12}$ probed by x-ray resonant elastic scattering

Abstract

The quadruple perovskite CaMn${}_7$O${}_{12}$ is a topical multiferroic, in which the hierarchy of electronic correlations driving structural distortions, modulated magnetism, and orbital order is not well known and may vary with temperature. x-ray resonant elastic scattering (XRES) provides a momentum-resolved tool to study these phenomena, even in very small single crystals, with valuable information encoded in its polarization- and energy-dependence. We present an application of this technique to CaMn${}_7$O${}_{12}$. By polarization analysis, it is possible to distinguish superstructure reflections associated with magnetic order and orbital order. Given the high momentum resolution, we resolve a previously unknown splitting of an orbital order superstructure peak, associated with a distinct \textit{locked-in} phase at low temperatures. A second set of orbital order superstructure peaks can then be interpreted as a second-harmonic orbital signal. Surprisingly, the intensities of the first- and second-harmonic orbital signal show disparate temperature and polarization dependence. This orbital re-ordering may be driven by an exchange mechanism, that becomes dominant over the Jahn-Teller instability at low temperature.

arXiv comment6 pages, 4 figures and 1 supplementary with 3 figures

References in corpus (11)

• Giant improper ferroelectricity in the ferroaxial magnet CaMn7O12
• Orbital ordering, Jahn-Teller distortion, and anomalous X-Ray scattering in Manganates
• Momentum-dependent charge correlations in YBa${}_2$Cu${}_3$O${}_{6+\delta }$ superconductors probed by resonant x-ray scattering: Evidence for three competing phases
• Multiferroic Properties of CaMn${}_7$O${}_{12}$
• Direct observation of orbital ordering in La${}_{0.5}$Sr${}_{1.5}$MnO${}_4$ using soft x-ray diffraction
• Transition between orbital orderings in YVO3
• Orbital Ordering in the Manganites :- Resonant X-ray Scattering Predictions at the Manganese L_II and L_III Edges
• The nature of Ho magnetism in multiferroic HoMnO3
• Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite
• Magnetic field induced transitions in multiferroic TbMnO3 probed by resonant and non-resonant X-ray diffraction
• Possible coupling between magnons and phonons in multiferroic CaMn7O12

Cited by in corpus (1)

• Magnetodielectric Properties in Two Dimensional Magnetic Insulators