Giant atomic displacement at a magnetic phase transition in metastable Mn3O4

Journal Article · Tue Jan 01 00:00:00 EST 2013 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.87.014417· OSTI ID:1087049

Hirai, Shigeto ^[1]; Moreira Dos Santos, Antonio F ^[2]; Shapiro, Max C ^[1]; Molaison, Jamie J ^[2]; Pradhan, Neelam ^[2]; Guthrie, Malcolm ^[3]; Tulk, Christopher A ^[2]; Fisher, Ian R ^[1]; Mao, Wendy ^[1]

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1. Stanford University
2. ORNL
3. Carnegie Institution of Washington

We present x-ray, neutron scattering, and heat capacity data that reveal a coupled first-order magnetic and structural phase transition of the metastable mixed-valence postspinel compound Mn3O4 at 210 K. Powder neutron diffraction measurements reveal a magnetic structure in which Mn3+ spins align antiferromagnetically along the edge-sharing a axis, with a magnetic propagation vector k = [1/2,0,0]. In contrast, the Mn2+ spins, which are geometrically frustrated, do not order until a much lower temperature. Although the Mn2+ spins do not directly participate in the magnetic phase transition at 210 K, structural refinements reveal a large atomic shift at this phase transition, corresponding to a physical motion of approximately 0.25 angstrom, even though the crystal symmetry remains unchanged. This "giant" response is due to the coupled effect of built-in strain in the metastable postspinel structure with the orbital realignment of the Mn3+ ion.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1087049
• Journal Information: Physical Review B, Vol. 87, Issue 1; ISSN 1098--0121
• Country of Publication: United States
• Language: English

Related Subjects

Magnetic Oxides
High Pressure
Neutron Scattering