Non-collinear magnetic structure of manganese quadruple perovskite CdMn7O12

Abstract

We report on the magnetic structure of CdMn7O12 determined by powder neutron diffraction. We were able to measure the magnetic structure of this Cd containing and highly neutron absorbing material by optimizing the sample geometry and by blending the CdMn7O12 with Aluminum powder. Below its Néel temperature TN1 all magnetic reflections can be indexed by a single commensurate propagation vector k = (0, 0, 1). This is different to the case of CaMn7O12 where the propagation vector is incommensurate and where an in-plane helical magnetic structure has been found. We observe a commensurate non-collinear magnetic structure in CdMn7O12 with in-plane aligned magnetic moments resembling the ones in CaMn7O12. However, the commensurate propagation vector prevents the appearance of a helical magnetic structure in CdMn7O12. Finally, we also observe a third structural phase transition below ~60 K that can be attributed to phase separation.

Magneto-orbital ordering in the divalent A -site quadruple perovskite manganites AMn7O12 ( A=<

“…The refined moment magnitudes are plotted in Figure 4b, and the magnetic structure is illustrated in Figure 5. Our results for the AFM1 phase are in good agreement with those previously published 33 . Below T N2 = 33K, the fundamental propagation vector de-locks from the orbital order propagation vector and monotonically increases towards the incommensurate ground state length (Figure 4a).…”

“…For completeness, we will begin with a repeat analysis of the AFM1 structure, and then continue with details of the AFM2 phase. We note that in the previous work 33 crystallographic phase separation was found below 60 K. We did not observe any such phase separation in the sample used in our neutron diffraction experiments, however, it was detected in another sample not reported here.…”

“…Our results are in good agreement with those published in reference 33 with the exception of the fractional coordinates of atom O1-1 (labelled O1 in Table 2 of ref. 33). In the previously published structure 33 this atom appears to deviate greatly from its nominal position in the higher symmetry R3 structure, and as a result bonding with its neighbours would be unphysical.…”

“…The magnetic structure of CdMn 7 O 12 in the AFM1 phase has been reported 33 , however, the AFM2 magnetic structure and coupling to the orbital physics had not been discussed. For completeness, we will begin with a repeat analysis of the AFM1 structure, and then continue with details of the AFM2 phase.…”

Spin-induced multiferroicity in the binary perovskite manganite Mn2O3

“…It could be due to extrinsic factors such as space trapped charges at grain boundaries. We note that a broad and high pyroelectric peak was often reported in the quadruple perovskite manganites such as CaMn 7 O 12 , and its origin is quite controversial 27,34–44 .

Fig. 5Spin-induced ferroelectricity in the binary perovskite Mn 2 O 3 .

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