Revisiting the magnetic structure of La_1/3Sr_2/3FeO₃ by neutron powder diffraction and Mössbauer spectroscopy

Abstract:

La_1/3Sr_2/3FeO₃ is reported to show a 2Fe⁴⁺ → Fe³⁺ + Fe⁵⁺ charge disproportionation (CD) accompanied by Fe³⁺/Fe⁵⁺ charge ordering (CO) and a metal-insulator (MI) transition at 200 K [1]. The MI transition was ascribed to CD and CO. Based on the CO, the magnetic structure was reported to be P-3m1 or P1 from the neutron diffraction studies performed at 50 K and 15 K, respectively [2]. The former seems not to be a correct solution since the presence of rotoinversion -3 is incompatible with the claimed collinear magnetic structure, with the collinear moments in the ab-plane in R-3c metric; and the latter might be a correct solution, but without any symmetry restrictions in space group P1. In this study, the magnetic ordering of this compound has been revisited by neutron powder diffraction and Mössbauer spectroscopy down to 2 K. From full symmetry analysis, a chiral helical model and a collinear model are proposed. The neutron diffraction pattern is equally well fitted by either model. The compatibility of the magnetic structure models with the Mössbauer spectroscopy results is discussed.

Reference
[1] Park S.K. et al., Phys. Rev. B. (1999) 60, 10788-10795.
[2] Battle P. D. et al., J. Solid State Chem. (1990) 84, 271-279; Yang J.B. et al., J. Phys.: Condens. Matter.(2003) 15, 5093-5102.