High-Pressure Synthesis, Crystal Structure, and Magnetic Properties of Sr₂MnO₃F: A New Member of Layered Perovskite Oxyfluorides

Abstract

We have successfully synthesized Sr2MnO3F, a new layered perovskite oxyfluoride with a n = 1 Ruddlesden-Popper-type structure using a high-pressure, high-temperature method. Structural refinements against synchrotron X-ray diffraction data collected from manganese oxyfluoride demonstrated that it crystallizes in a tetragonal cell with the space group I4/mmm, in which the Mn cation is located at the octahedral center position. This is in stark contrast to the related oxyhalides that have square-pyramidal coordination such as Sr2MO3X (M = Fe, Co, Ni; X = F, Cl) and Sr2MnO3Cl. There was no evidence of O/F site order, but close inspection of the anion environment centered at the Mn cation on the basis of bond-valence-sum calculation suggested preferential occupation of the apical sites by the F ion with one oxide ion in a random manner. Magnetic susceptibility and heat capacity measurements revealed an antiferromagnetic ordering at 133 K (=TN), which is much higher than that of the chloride analogue with corrugated MnO2 planes (TN = 80 K).

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi2TiO4F2

“…In terms of lattice mismatch, F occupancy of equatorial X 1 sites might be expected (giving perovskite blocks of a similar width to the [Bi 2 O 2 ] 2+ layers) but tilting of the Ti X 6 octahedra, about in-plane and out-of-plane axes, can also reduce this interfacial mismatch while maintaining satisfactory Ti– X bond lengths. The bond valence sum analysis and our understanding of strain suggest that F occupancy of equatorial X 1 sites is certainly possible in Bi 2 TiO 4 F 2 and is consistent with the conclusions of Needs et al 39 However, this contrasts with several other n = 1 Aurivillius and Ruddlesden-Popper oxyfluorides including Bi 2 NbO 5 F, 54 Sr 2 ScO 3 F, 67 and Sr 2 MnO 3 F, 68 which are reported to have F occupancy of apical anion sites despite similar arguments involving stacking strain between [Bi 2 O 2 ] 2+ and Nb(O,F) 2 layers ( a p = 3.95 Å and a p = 4.08 Å for F – in equatorial X 1 or apical X 2 sites, respectively) or between SrO and Mn(O,F) 2 layers (ideal a SrO ≈ 3.65 Å; for Sr 2 ScO 3 F a p = 4.12 Å and a p = 4.19 Å for F – in equatorial or apical sites, respectively; for Sr 2 MnO 3 F a p = 3.86 Å and a p = 3.99 Å for F – in equatorial or apical sites, respectively). It is striking that Bi 2 TiO 4 F 2 has relatively small stacking strain compared to these examples, suggesting the possibility that anion distribution might be tuned by strain engineering, for example.…”

Uncovering anisotropic magnetic phases via fast dimensionality analysis

“…49 Given the similarity in cation-anion coordination in Figure 3(a), it becomes clear that an opportunity arises to form V analogs of the more numerous magneticallysquare-planar Mn fluorides, for example to produce NaRb 2 V 3 F 12 , Sr 2 VO 3 F, or LiVF 4 •H 2 O (corresponding to Mn-based ICSD codes 83871, 291640, and 417512, respectively). [50][51][52] Similar logic can be applied to the landscape around Rb 2 CrCl 2 I 2 , which is the only such compound in the Cr-I system. 53 Searching for hexagonal/kagomé ordering (metalmetal-metal angle 55 • -65 • ) again shows a high prevalence for oxides in Figure 6(b).…”

Exploring novel functional properties arose from anion order in mixed anion compounds

“…For simple perovskites oxyfluorides, O 2¹ and F ¹ are disordered; SrFeO 2 F, 3) BaFeO 2 F 4) PbScO 2 F 5) BaScO 2 F 6) AgFeOF 2 7) BaInO 2 F 8) and AgTiO 2 F 9) adopt the cubic or nearly cubic perovskite structure, in which O 2¹ and F ¹ occupy the same crystallographic sites and are randomly distributed. However, in a variety of RuddlesdenPopper type layered perovskites such as Sr 2 CuO 2 F 2 , 10) Sr 2 FeO 3 F, 11),12) Ba 2 InO 3 F, 13) Ba 2 ScO 3 F, 14) Sr 2 MnO 3 F, 15) Sr 3 Fe 2 O 5¹x F y 11), 16) and the others, 17) the F ¹ ions occupy selectively the interlayer site. This manner leads O/F order, but their degrees of ordering are different.…”