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

Journal article

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.

Authors: Johnson, R; Khalyavin, D; Manuel, P; Bombardi, A; Martin, C

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review B
• Volume: 93
• Issue: 18
• Pages: 180403
• Publication date: 2016-05-01
• Acceptance date: 2016-04-26
• DOI: 10.1103/PhysRevB.93.180403
• ISSN: 2469-9950 and 2469-9969
• Keywords: cond-mat.str-el; Journal Article