Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite

Abstract

Through a combination of neutron diffraction and Landau theory we describe the spin ordering in the ground state of the quadruple perovskite manganite CaMn7O12 - a magnetic multiferroic supporting an incommensurate orbital density wave that onsets above the magnetic ordering temperature, TN1 = 90 K. The multi-k magnetic structure in the ground state was found to be a nearly-constant-moment helix with modulated spin helicity, which oscillates in phase with the orbital occupancies on the Mn3+ sites via trilinear magneto-orbital coupling. Our phenomenological model also shows that, above TN2 = 48 K, the primary magnetic order parameter is locked into the orbital wave by an admixture of helical and collinear spin density wave structures. Furthermore, our model naturally explains the lack of a sharp dielectric anomaly at TN1 and the unusual temperature dependence of the electrical polarisation.

arXiv commentAccepted for publication in Physical Review B, Rapid Communications

References in corpus (4)

• Giant improper ferroelectricity in the ferroaxial magnet CaMn7O12
• Jahn-Teller distortions and charge, orbital and magnetic orders in NaMn7O12
• Commensurate structural modulation in the charge- and orbitally-ordered phase of the quadruple perovskite (NaMn${}_3$)Mn${}_4$O${}_{12}$
• First-principles study of structurally modulated multiferroic CaMn${}_7$O${}_{12}$

Cited by in corpus (10)

• Universal magneto-orbital ordering in the divalent $A$-site quadruple perovskite manganites $A$Mn${}_7$O${}_{12}$ ($A$ = Ca, Sr, Cd, and Pb)
• The magnetic structure and spin-flop transition in the A-site columnar-ordered quadruple perovskite $\mathrm{TmM}{\mathrm{n}}_3{\mathrm{O}}_6$
• Soft phonon driven orbital order in CaMn7O12
• Ferroelectricity in the 1 $\mu$C cm${}^{-2}$ range induced by canted antiferromagnetism in (LaMn${}_3$)Mn${}_4$O${}_{12}$
• Improper magnetic ferroelectricity of nearly pure electronic nature in cycloidal spiral CaMn${}_7$O${}_{12}$
• Unusual effects of magnetic dilution in the ferrimagnetic columnar ordered $\mathrm{S}{\mathrm{m}}_2\mathrm{MnMnM}{\mathrm{n}}_{4-\mathrm{x}}\mathrm{T}{\mathrm{i}}_{\mathrm{x}}{\mathrm{O}}_{12}$ perovskites
• Neutron powder diffraction study of NaMn${}_2$O${}_4$ and Li${}_{0.92}$Mn${}_2$O${}_4$: New insights on spin-charge-orbital ordering
• Magnetic transitions in CaMn7O12 : a Raman observation of spin-phonon couplings
• Competing electronic instabilities in the quadruple perovskite manganite PbMn${}_7$O${}_{12}$
• Magnetic and orbital correlations in multiferroic CaMn${}_7$O${}_{12}$ probed by x-ray resonant elastic scattering