CORRIGENDUM: Crystal, magnetic, and electronic structures, and properties of new BaMnPnF (Pn = As, Sb, Bi)

New BaMnPnF (Pn = As, Sb, Bi) are synthesized by stoichiometric reaction of elements with BaF2. They crystallize in the P4/nmm space group, with the ZrCuSiAs-type structure, as indicated by X-ray crystallography. Electrical resistivity results indicate that Pn = As, Sb, and Bi are semiconductors with band gaps of 0.73 eV, 0.48 eV and 0.003 eV (extrinsic value), respectively. Powder neutron diffraction reveals a G-type antiferromagnetic order below TN = 338(1) K for Pn = As, and below TN = 272(1) K for Pn = Sb. Magnetic susceptibility increases with temperature above 100 K for all the materials. Density functional calculations find semiconducting antiferromagnetic compounds with strong in-plane and weaker out-of-plane exchange coupling that may result in non-Curie Weiss behavior above TN. The ordered magnetic moments are 3.65(5) μB/Mn for Pn = As, and 3.66(3) μB/Mn for Pn = Sb at 4 K, as refined from neutron diffraction experiments.


Results
Synthesis, crystal chemistry, and stability. Three new compounds of BaMnAsF, BaMnSbF and BaMnBiF are synthesized using the solid-state sintering method. The compounds crystallize in the primitive ZrCuSiAs-type tetragonal P4/nmm (No. 139, Pearson symbol tP8), and are isotypic to the lighter BaMnPF (Figure 1) 15 .
EDS results confirm the presence of small crystallites with BaMnSbF and BaMnBiF compositions after the first heating step, which allows for collection of single-crystal x-ray diffraction data (Table 1). There are four crystallographically unique atoms in the asymmetric unit cell, all located in special positions (Tables 2, 4, S1). BaMnPnF structure, similar to LaFeAsO, can be viewed with cationic 2 ? [BaF] 1 and anionic 2 ? [MnPn] 2 layers alternating along the c-axis. These layers are built upon edge-sharing FBa 4 and MnPn 4 tetrahedra, respectively. Following the discovery of superconductivity in the F-doped LaFeAsO, the ZrCuSiAs-type structure and its relationship with other structures have been extensively studied 11,22,23 .
From single crystal X-ray data (Table 3) (2)u, from the room temperature PXRD data (see Table  S1). The bond distances and angles in BaMnPnF are very close to those reported for the related BaMn 2 Pn 2 ternary phases [24][25][26] , which also contain anionic 2 ? [MnPn] 2 layers. PXRD patterns along with Rietveld refinements results for BaMnAsF, BaMnSbF and BaMnBiF are illustrated in Figures 2 to 4. There are no Bragg peaks in the 2h range of 5-20u for Pn 5 As and Sb, and so the low angle regions are not shown for them. The broad background below 2h , 25u in Pn 5 Sb and Bi (Figure 3-4) are caused by the polycarbonate cover. X-ray diffraction refinement detects a small amount of BaF 2 crystalline impurity (less than 1% by mass) in Pn 5 As and Bi products, whereas no impurity peaks are observed in the Pn 5 Sb compound.
All BaMnPnF samples have MnO impurities if ground in air during sample sintering stages. Even in the final product form, groundin-air BaMnSbF shows signs of oxidation in the PXRD data, while BaMnBiF burns in air. The extreme air sensitivity of ground BaMnBiF limits its full characterization through neutron diffraction experiments. Notwithstanding these facts, the heating of pellets under ambient conditions up to 130uC and subsequent PXRD measurements demonstrate that BaMnPnF are air-stable in pellet form.
The refined room temperature lattice parameters from the PXRD data are a 5 4.2739(1) Å and c 5 9.5875(2) Å for BaMnAsF (Rp 5 8.54%, wRp 5 11.52%), a 5 4.4791(1) Å and c 5 9.8297(2) Å for BaMnSbF (Rp 5 4.59%, wRp 5 6.03%), and a 5 4.5384(1) Å and c 5 9.8929(2) Å for BaMnBiF (Rp 5 4.05%, wRp 5 5.40%). The refinement of PXRD data on BaMnAsF and BaMnSbF show (Figures 2b, and P~(F 2 o z2F 2 c )=3; A and B are weight coefficients.   Table 1) are the largest within this structure type along with that of BaCdSbF 18 . As expected from the large unit cell volumes and lattice parameters of BaMnSbF and BaMnBiF, the bond distances are also longer than those reported for other compounds that adopt this structure type 8,11 . The thermal behaviors of BaMnAsF and BaMnSbF are studied through TGA/DTA ( Figure S1). Both BaMnAsF and BaMnSbF are stable up to 1300 K (,1030uC), after which they decompose. Additionally, pellets of BaMnAsF and BaMnSbF are separately vacuum sealed inside silica tubes and heated to 1500 K with periodic visual monitoring. This is done because the DTA on BaMnAsF ( Figure S1) shows two peaks upon heating, and it is not immediately clear if the first peak corresponds to the melting of the compound. No visual change occurs to the pellets up to ,1430 K, after which molten liquid is clearly visible in both samples. These molten pieces contain MnAs and MnSb binaries according to the EDS results.
Physical properties. For BaMnPnF, temperature dependence of electrical resistivity results are plotted in Figure 5. The compounds show semiconducting behavior, with room temperature resistivity values of r 300K (BaMnAsF) 5 3.6 3 10 5 V cm, r 300K (BaMnSbF) 5 2.4 3 10 4 V cm, and r 300K (BaMnBiF) 5 0.135 V cm. Similarly, BaMnPF is also reported as a semiconductor 15 . The semiconducting behavior supports the charge-balanced nature of the compounds according to [Ba 21 F 2 ][Mn 21 Pn 32 ]. dr/dT derivatives of the resistivity data are featureless in the measured range. Calculated band gaps from the Arrhenius fit (lnr 5 lnr 0 1 E g /2k B T) are E g (BaMnAsF) 5 0.73 eV, E g (BaMnSbF) 5 0.48 eV, and E g (BaMnBiF) 5 0.003 eV (see Figure 5). These band gap values follow the expected periodic trend based on electronegativities of pnictogen elements 28 . It is interesting that for BaMnBiF, both the temperature dependence of electrical resistivity and the calculated narrow band gap are quite different when compared to the other Pn members. For BaMnBiF, r(T) decreases upon cooling down to ,85 K, then changes slope and sharply increases below 80 K. From the trend in the band gaps in this family, it can be speculated that BaMnBiF is an extrinsic semiconductor 29 .
The calculated band gaps for BaMnAsF and BaMnSbF are two orders of magnitude larger than those reported for the narrow gap semiconductors of BaMn 2 Pn 2 , with band gaps of 6-54 meV [24][25][26] . Such a difference may be attributed to the fact that BaMnPnF contain an additional insulating [BaF] 1 layer in the structure, which reduces the band dispersion in the c-axis direction. Further comparisons can be made with the isostructural quaternary phases based on manganese. Most of LnMnPnO (Ln 5 rare-earth metal) compositions have been reported to be semiconductors with varying band gaps 11 , with exceptions such as metallic PrMnSbO 30 .
Temperature-and field-dependent magnetization results for BaMnAsF are plotted in Figure 6a. ZFC and FC x(T) data overlap for BaMnAsF, and are measured up to ,800 K. There is an upward tail in x(T) below ,15 K, which is probably due to paramagnetic impurities, above which magnetic susceptibility increases slowly with rising temperature. There is another change in the slope of x(T) at ,550 K, above which x(T) starts to plateau. M(H) plots both at 5 K and 100 K are linear. x(T) and M(H) data, coupled with resistivity data, suggest that BaMnAsF is likely a local moment antiferromagnet.   The long range antiferromagnetic order found from neutron diffraction results (see next section) at T N 5 338(1) K for BaMnAsF, and T N 5 272(1) K for BaMnSbF do not manifest clearly in the magnetic susceptibility data ( Figure 6). Magnetic susceptibility data without a feature at T N is not unique to BaMnAsF and BaMnSbF; for example, x(T) for LaMnPO 31 (T N 5 375(5) K) is featureless up to 800 K; this was attributed to a very strong exchange coupling in the compound. Cases of increasing x(T) above T N have also been reported for BaMn 2 As 2 32 , BaMn 2 Bi 2 26 , BaFe 2 As 2 3 and LaFeAsO 33 .
Neutron powder diffraction. Results of the neutron powder diffraction (NPD) experiments are summarized in Table 4, and Although lower than expected, the ordered moment values of 3.65(5) m B /Mn for BaMnAsF, and 3.66(3) m B /Mn for BaMnSbF suggest local moment antiferromagnetism in these compounds. In comparison, the ordered moment values are 0.2-1.0 m B /Fe in the delocalized spin-density-wave (SDW) antiferromagnets of AEFe 2 As 2 34 and LnFeAsO 22 . Reduced moments and G-type ordering have also been reported for BaMn 2 P 2 (4.2(1) m B /Mn) 35 and BaMn 2 As 2 (3.88(4) m B /Mn) 34 . Among the quaternary ZrCuSiAstype compounds of Mn, the ordered moments are 3.28(5) m B /Mn for LaMnPO (AF in the [MnP] 2 layer and ferromagnetic, F, between the layers) 31 , 3.34(2) m B /Mn for LaMnAsO (intralayer AF and interlayer F) 36 , and ,3 m B /Mn for PrMnSbO (AF C-type) 30 . For these compounds, the reduced ordered moments have been attributed to a strong hybridization between pnictogen p and Mn d orbitals 10,37 .  29 . It is interesting that temperature dependence of the refined lattice parameters of BaMnAsF (Figure 7b) show a nonlinear trend around room temperature; this may be indicative of a magnetoelastic coupling in BaMnAsF.
Electronic structure calculations. All three compounds are found to be strongly magnetic with substantial Mn moments, in spite of the strong covalency between Mn and pnictogens. We perform calculations for both ferromagnetic (F) and in-plane nearest-neighbor   antiferromagnetic (AF) spin configurations for the materials and consider additional magnetic configurations for BaMnAsF. In all cases, the AF configuration was lower in energy than the F configuration. The energy differences between the two configurations are 0.48 eV/f.u for BaMnAsF, 0.37 eV/f.u for BaMnSbF, and 0.33 eV/f.u for BaMnBiF. These energies are extremely high and indicate high magnetic ordering temperatures. For comparison, the prototypical ferromagnet, bcc Fe (T C 5 1043 K), has a F -AF energy difference of ,0.4 eV in density functional calculations 38 .
The qualitative reasons for these high energies may be seen in the electronic structures. The calculated densities of states for BaMnAsF for the in-plane AF order are shown in Figure 9, with the corresponding band structures in Figure 10 (the plots for BaMnSbF and BaMnBiF are provided in Figures S5-S6). The fluorine and barium atoms are fully ionic, and the resulting ionic [BaF] 1 layers form insulating barriers between the [MnPn] 2 layers in the crystal structure as is seen in the relatively weak dispersion of the occupied bands along the c-axis (C-Z) in Figure 10. As may be seen, the band structures with this magnetic order are semiconducting. The calculated gaps are 0.70 eV, 0.56 eV and 0.42 eV for BaMnAsF, BaMnSbF and BaMnBiF, respectively. The values for BaMnAsF and BaMnSbF are close to those found from transport data, which is the expected behavior of a material where the gap is between different transition metal d-manifolds and where Mott-Hubbard type Coulomb correlations are not large 39 . This is in contrast to simple semiconductors where DFT gaps are underestimates and especially Mott-Hubbard insulators where DFT calculations give either no gaps or gaps much smaller than experiment. The inferred relative weakness of Mott-Hubbard correlation effects in these materials is reminiscent of the FeSCs, although it should be noted that this does not mean that the FeSCs are uncorrelated 40,41 .
We find very strong covalency between the spin polarized Mn d orbitals and the pnictogen p orbitals in all three compounds. This is seen in the electronic densities of states for the nearest neighbor antiferromagnetic state ( Figure 9). As may be seen from the projections the hybridization is strongly spin dependent, providing an explanation for the high energy scale associated with magnetic order. This is further seen by comparing the calculated electronic structures for the F and AF order. Figure 11 compares the Mn d projection of the spin resolved density of states (DOS) for BaMnAsF with these two orders. There is a strong reconstruction of the electronic structure when going to the less favorable F order. In fact, this reconstruction is so strong that the semiconducting gap is closed and because of this the magnetization is reduced from the nominal value of 5 m B /Mn to lower values of 4.0 m B , 4.3 m B and 4.4 m B for BaMnAsF, BaMnSbF and BaMnBiF, respectively (calculated based on the total spin magnetization in the cell, not the moments in LAPW spheres). As discussed e.g. by Goodenough 42 , cases where the covalency and electronic structure are strongly affected by magnetic order are cases where high exchange couplings can be expected.
In general local moment magnetism has two ingredients: (1) moment formation and (2) the interactions between the moments   that lead to order. While divalent Mn can occur in different spin states depending on the strength of the hybridization with ligands, here we find a near high spin case for all the magnetic orderings considered with similar spin moments in the Mn LAPW spheres for the F and AF cases (as well as the other cases for BaMnAsF). However, the energy associated with moment formation is not so much smaller than the ordering energy. For BaMnAsF in particular, non-spin-polarized calculations (no moments) yield an energy 1.27 eV/f.u. higher than the nearest neighbor AF order, i.e. less than three times higher than the F order (0.48 eV/f.u.).
Consistent with this, we find very weak magnetic interactions in the c-axis direction. For BaMnAsF, we calculated the energy for doubled cells along c-axis for the F and in-plane AF cases with and without alternation of spins along the c-axis. The energy differences were below 1 meV per formula unit implying that this is a very highly two dimensional magnetic system.
In the case of BaMnAsF, we also considered other AF in-plane configurations. These were for the order observed in the Fe-pnictides consisting of chains of like spin Mn atoms (the so-called SDW order) and the double stripe pattern found in FeTe 43 (see Ref. 43 for a depiction of these orders). On a per formula unit basis, we find that the SDW type ordering and the double stripe ordering are 0.12 eV and 0.21 eV higher than the nearest neighbor AF order, respectively. Therefore, in agreement with the NPD data, we conclude that the nearest neighbor in-plane order is the probable ground state.
As mentioned, our calculations included spin orbit. In this case the energy depends on the spin orientation through the magnetocrystalline anisotropy. While this energy is small compared to the ordering energy, it is relevant to the magnetic behavior. For BaMnAsF, we did calculations with the moments oriented in the a-axis direction as well along the c-axis direction. For the other cases discussed, the calculations are done with the moments along the c-axis. With the experimental crystal structure the uniaxial c-axis direction is favored by 1.0 meV/f.u.. While this is a small energy, if correct, the result implies that there will not be a strong Kosterlitz-Thouless type reduction in the ordering temperature due to the near 2D character of the material. To summarize, the calculations find that these materials are local moment antiferromagnetic semiconductors with moderate band gaps and strong spin-dependent hybridization between the Mn d states and the pnictogen p states. The materials are rather two dimensional both electronically and magnetically. The strong hybridization leads to reconstructions of the band structure with changes in  magnetic order. This in turn underlies very high magnetic energy scales consistent with high T N that are confirmed in neutron diffraction.

Discussion
Three new 1111 fluoropnictides with the ZrCuSiAs-type structure, namely BaMnAsF, BaMnSbF and BaMnBiF, are synthesized by reacting elements with BaF 2 . The initial reactions of these components give small plate crystallites that are suitable for structure refinements using single crystal X-ray diffraction. Subsequent two-step annealing procedure results in approximately single-phase products (,2% impurity content from PXRD and magnetization results). For BaMnPnF, the unit cell volumes and bond distances are much larger compared to the isostructural Mn-based oxypnictides.
Temperature dependence of electrical resistivity suggest that BaMnPnF are semiconductors with band gaps of E g (BaMnAsF) 5 0.73 eV, E g (BaMnSbF) 5 0.48 eV, and E g (BaMnBiF) 5 0.003 eV. These values are comparable to the theoretical gaps of 0.70 eV for BaMnAsF and 0.56 eV for BaMnSbF, but not 0.42 eV for BaMnBiF. The large discrepancy in the band gap for BaMnBiF derived from the resistivity data is likely due to the influence of doping. Based on electronic structure calculations, BaMnPnF are strongly magnetic with a preferred G-type antiferromagnetic ground state. Neutron powder diffraction (NPD) results give evidence for the G-type antiferromagnetic order below T N 5 338(1) K for BaMnAsF, and T N 5 272(1) K for BaMnSbF. However, temperature dependence of magnetization x(T) data on these polycrystalline pellets show no anomalies at T N , and x(T) increase with increasing temperature above T N . Similar featureless x(T) data and non-Curie-Weiss behavior was recently reported for LaMnPO 31 , and increasing x(T) above ordering temperatures are observed for BaMn 2 As 2 32 , BaMn 2 Bi 2 26 , BaFe 2 As 2 3 and LaFeAsO 33 . Such behavior may be indicative of strong exchange coupling among Mn moments in BaMnPnF. Another important feature of BaMnPnF phases is a strong hybridization between Mn and Pn states, which is responsible for reduced ordered moment values of 3.65(5) m B /Mn for BaMnAsF, and 3.66(3) m B /Mn for BaMnSbF, as determined from the NPD data at 4 K. The observed semiconducting antiferromagnetic behavior of BaMnPnF (Pn 5 As, Sb and Bi) is similar to the reported behavior in Mn-based oxypnictides LnMnPnO (Ln 5 La-Sm; Pn 5 P, As) 11 .
In conclusion, further studies of transition-metal-based ZrCuSiAstype compounds in general, and BaMnPnF in particular, are warranted. Although electronic structures of BaMnPnF are not similar to that of the superconducting Fe-based 1111 compounds, recent reports show that 1111 phases may demonstrate interesting variation of electrical and magnetic properties with doping and under applied pressure; for example, antiferromagnetic insulator LaMnAsO turns ferromagnetic metal when doped with hydrogen 44 . Another Mnbased compound, LaMnPO, transforms from an AF insulator to an AF correlated metal under pressure 31 . In addition, there is continued interest in 1111 phases due to the recent discovery of a high thermoelectric efficiency in BiCuSeO, which is further enhanced by introduction of Cu defects 27 .

Methods
Synthesis. Dendritic Ba, Mn and As pieces, and Sb and Bi granules with purities greater than 99.9% are used as received from Alfa Aesar. Ultrapure BaF 2 powder, from Ventron Alfa Inorganics, is dried at 200uC for 3 h before using. Reactants in the stoichiometric ratio of Ba5BaF 2 5Mn5Pn 5 1515252 are weighed inside a heliumfilled glovebox and put into alumina crucibles. The alumina crucibles are then transferred into silica tubes and sealed under vacuum. The reaction mixtures are heated to 1000uC (30uC h 21 ; dwell 6 h), then to 900uC (10uC h 21 ; dwell 6 h), and subsequently to 300uC (30uC h 21 ) after which the furnaces are switched off. This initial sintering step produced multi-phase reaction products, along with mm-size crystallites of 1111 phase in Pn 5 Sb and Bi, which are extracted for structural determinations using single crystal X-ray diffraction. The products are reground and pelletized inside the glovebox. The pellets are then placed inside alumina crucibles, enclosed in silica tubes, vacuum sealed, then annealed for a second time at 900uC (dwell 60 h). The third sintering step is the repeat of the latter annealing procedure. This only results in marginal improvement of phase purity as judged by slightly lower BaF 2 impurity levels compared to the second sintering step.
Characterization. X-ray diffraction. For BaMnPnF (Pn 5 As, Sb, Bi), powder X-ray diffraction (PXRD) data are collected on a PANalytical X9Pert PRO MPD X-ray Diffractometer using monochromated Cu-Ka 1 radiation. Scans are performed in 5-65u (2h) range, with a step size of 1/60u and 20-100 seconds/step counting time. Low temperature data collections are carried out using an Oxford Phenix closed cycle cryostat. Due to the air sensitivity of finely ground powders of Pn 5 Sb and Bi, the powders are loaded in a protective holder with a polycarbonate cover, inside the    For Pn 5 Sb and Bi, single crystal x-ray diffraction data are collected on a Bruker SMART APEX CCD-based diffractometer, which employs Mo Ka radiation (l 5 0.71073 Å ). Crystals are selected under a microscope and cooled to 173(2) K under a cold nitrogen stream. The data collection, data integration and refinement are carried out using the SHELXTL software package 47 . SADABS is used for semi-empirical absorption correction based on equivalents. The structures are solved by direct methods and refined by full matrix least-squares methods on F 2 . All sites are refined with anisotropic atomic displacement parameters and full occupancies. Details of the crystallographic data and structure refinement parameters are given in Table 1. Positional and equivalent isotropic displacement parameters, along with refined interatomic distances and angles are provided in Tables 2 and 3 Thermal analysis. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) on BaMnPnF (Pn 5 As, Sb) are performed using a Pyris Diamond TG/ DTA from Perkin Elmer, under a stream of ultra-high purity argon gas. The measurements are carried out on 20-25 mg pellet pieces in the temperature interval of 323-1573 K (20 K min 21 ).
Neutron powder diffraction. Neutron powder diffraction experiments on BaMnPnF (Pn 5 As and Sb) are carried out using the HB-2A neutron powder diffractometer at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). Measurements are performed using two different wavelengths of l 5 1.536 Å and 2.410 Å provided by the (115) and (113) reflections of a vertically focusing Ge monochromator; this allows for optimization of the instrument resolution function for specific Q ranges. The data are collected by scanning the detector array consisting of 44 3 He tubes in two segments to cover the total 2h range of 6-150u in steps of 0.05u; overlapping detectors for the given step average the counting efficiency of each detector 48 . For the measurements, 4 g powder samples are confined inside vanadium containers. For below room temperature measurements, samples are loaded inside a JANIS top-loading closed-cycle refrigerator, while for high temperatures experiments up to 800uC, samples are loaded in an ILL vacuum furnace equipped with Nb heating elements. Rietveld refinements are performed using the FULLPROF program 49 . Spin configurations compatible with the crystal symmetry are generated by group-theory analysis using the program SARAh 50 . In Pn 5 As compound, impurity phases of BaF 2 (1.5% weight fraction) and Mn 2 As (2.5%) are noted; in Pn 5 Sb compound, BaF 2 (2.5% weight fraction) and Mn 12x O (2.4%) impurities are found.
Electronic structure calculations. First principles calculations are performed using the experimental crystal structure information data. The calculations are done within DFT using the generalized gradient approximation (GGA) of Perdew, Burke and Ernzerhof 51 and the general potential linearized augmented planewave (LAPW) method 52 as implemented in the WIEN2k code 53 . Well-converged basis sets and Brillouin zone samplings are employed, along with LAPW sphere radii of 2.4 Bohr for Ba, Mn, As, Sb and Bi, and 1.9 Bohr for F. Local orbitals 54 are added to the basis to include semi-core states and spin-orbit is included in the calculations. The labels and title of the x-axis of Figure 9 are omitted in this Article. The correct Figure 9 appears below as Figure 1.