Neutron powder diffraction study of NaMn2O4 and Li0.92Mn2O4 : Insights on spin-charge-orbital ordering

QC 20221124
High-pressure synthesized quasi-one-dimensional NaMn2O4 and Li0.92Mn2O4 are both antiferromagnetic insulators. Here their atomic and magnetic structures are investigated using neutron powder diffraction. The present crystal structural analyses of NaMn2O4 reveal that a Mn3+/Mn4+ charge-ordering state exists even at low temperature (down to 1.5 K). It is evident that one of the Mn sites shows a strongly distorted Mn3+ octahedron due to the Jahn-Teller effect. Above TN=35 K, a two-dimensional short-range correlation is observed, as indicated by asymmetric diffuse scattering. Below TN, two antiferromagnetic transitions are observed: (i) a commensurate long-range Mn3+ spin ordering below TN1=35 K and (ii) an incommensurate Mn4+ spin ordering below TN2=11 K. Surprisingly, the two antiferromagnetic orders are found to be independent of each other. The commensurate magnetic structure (kC=0.5,0.5,0.5) follows the magnetic anisotropy of the local easy axes of Mn3+, while the incommensurate Mn4+ one shows a spin-density-wave or a cycloidal order with kIC=(0,0,0.216). For Li0.92Mn2O4, on the other hand, the absence of a long-range spin-ordered state is confirmed down to 1.5 K.

NATURVETENSKAP Kemi Oorganisk kemi hsv//swe
NATURAL SCIENCES Chemical Sciences Inorganic Chemistry hsv//eng
Binary alloys; Crystal atomic structure; Crystallography; Density (optical); Magnetic anisotropy; Magnetic structure; Neutron powder diffraction; Spin density waves; Temperature

Nocerino, ElisabettaKTH,Material- och nanofysik(Swepub:kth)u13bhkxl (author)
Kamazawa, K. (author)
Forslund, Ola KenjiKTH,Material- och nanofysik(Swepub:kth)u1l2zla5 (author)
Sassa, Y. (author)
Keller, L. (author)
Sikolenko, V. V. (author)
Pomjakushin, V. (author)
Sakurai, H. (author)
Sugiyama, J. (author)
Månsson, Martin,As. Prof.1976-KTH,Material- och nanofysik(Swepub:kth)u1sajjx0 (author)
KTHMaterial- och nanofysik (creator_code:org_t)

By the author/editor: Matsubara, Nami; Nocerino, Elisab ...; Kamazawa, K.; Forslund, Ola Ke ...; Sassa, Y.; Keller, L.; show more...; Sikolenko, V. V.; Pomjakushin, V.; Sakurai, H.; Sugiyama, J.; Månsson, Martin, ...; show less...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Chemical Science ...; and Inorganic Chemis ...

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