Ion Sublattice Research Articles

From LaCrO3 towards LaCr0.2Mn0.2Fe0.2Al0.2Ga0.2O3 high-entropy ceramic compound: Crystal structure, dielectric and magnetic properties

A group of five perovskite-type ceramic systems was designed by solid-state reaction, increasing the configurational entropy, ΔSconf at the B-site, going from low and medium to finally reaching a high-entropy system. Chemical elements, crystal structure, and microstructure characterization, as well as the dielectric and magnetic properties, are discussed from the single phase LaCrO3 towards a continuous equiatomic multicomponent LaCr0.2Mn0.2Fe0.2Al0.2Ga0.2O3 ceramic compounds. Through a combination of structural analysis and XPS spectroscopy study, it is found that not only the configurational entropy ∆Sconf term, but also the enthalpy of mixing, ΔHmix through of arising of the coexistence of mixed valence state, oxygen vacancies, and local octahedral distortions lead to the stabilization of the single phase in equimolar multicomponent perovskite systems. The arising of Cr3+/Cr6+ and Mn3+/Mn2+ mixed valence state drives the AC electric conductivity through the presence of two kinds of charge carriers, small polarons and oxygen vacancies in LCM, LCMF, LCMFA, and LCMFAG ceramic compounds. The occurrence of these two classes of charge carriers progressively increases the AC electric conductivity at room and high temperatures for each ceramic compound, being higher for the LCMFA entropy compound, making it a potential candidate for solid oxide fuel cell (SOFC) applications. As expected, the increases of compositional random cations display rich magnetic properties arising from competing magnetic interactions driven by the sublattice of Cr, Mn, and Fe magnetic ions. The resulting ΔSconf increase leads to a Griffith-like phase. The results also show that not only the ferromagnetic clusters of the LaMnO3 (AxFz) sublattice but also the weak ferromagnetism associated with the LaCrO3 (GxFz), and LaFeO3 (GxFz) sublattices play a predominant role in the formation of the Griffiths-like phase in the low, medium and high-entropy ceramic systems.

Ab Initio Molecular Dynamics Simulation of the Superionic State in Pb0.78Sr0.19K0.03F1.97 Solid Solution: Behavioral Features of the Fluorine Ion Sublattice

Ab Initio Molecular Dynamics Simulation of the Superionic State in Pb0.78Sr0.19K0.03F1.97 Solid Solution: Behavioral Features of the Fluorine Ion Sublattice

Magnetothermal properties including magnetocaloric performance of the ternary rhombohedral Laves phase of Pr2Rh3Ge

The article presents the study of the magnetocaloric effect (MCE) for the rhombohedral Laves phase of Pr2Rh3Ge, which shows a magnetic order below TC=8.5 K. We have established that the compound exhibits a continuous second-order type of transition which was demonstrated and confirmed by several different techniques, mainly by analyzing universal curves of normalized entropy change as a function of scaled temperature. The observed MCE, in our opinion, is a consequence of an indirect exchange coupling between the magnetic sublattices of the rare earth ions, which, however, does not exclude the potential contribution of sublattice-containing transition metals. In this paper, the procedure to evaluate the MCE from magnetization and specific heat data is described. As a result, important parameters such as the isothermal magnetic entropy change (ΔSM), adiabatic temperature change (ΔTad), relative cooling power (RCP), and the temperature averaged entropy change (TEC) were determined. The highest values of −ΔSM, ΔTad, and RCP for a field change (Δμ0H) of 5 T at TC are 5.96 J/kgK, 3.87 K, and 72.62 J/kg, respectively. These results obtained for Pr2Rh3Ge seem to be, however, low compared to the values obtained for the rhombohedral Laves phases, belonging to the group of ternary germanides RE2Rh3Ge containing heavy rare earth metals (RE = Gd, Tb, Ho, and Er). Nevertheless, we believe that the results presented in this work extend and complement the current knowledge on the magnetocaloric properties of this family of materials.

Study of the influence of gamma irradiation on ferrite-spinel monocrystals

The mechanisms of redistribution of metal ions and the formation of defects in ferrite spinel upon irradiation are complex and depend on a number of factors. Therefore, computer simulations and experimental studies are important for understanding the behavior of the physical properties of these materials under the influence of radiation. The development of new materials that can withstand radiation damage is of great importance for a range of applications, including solid state physics, nuclear physics, space research and medical applications. In this work, the effect of gamma irradiation on Co0,75Cu0,25Fe2O4 ferrite single crystals has been investigated. An earlier study using Mössbauer spectroscopy was carried out to determine the changes in the metal ion content in the sublattices of ferrite spinels. These changes affect the magnetic crystallographic anisotropy of the material [1]. Data can be found in the scientific literature that indicate that gamma irradiation leads to changes in the magnetic susceptibility of materials and to changes in the magnetization curve [2,3]. These changes in physical properties can be explained by redistribution of metal ions in octahedral and tetrahedral sublattices, since metal ions in sublattices have splitting of atomic levels.

A New Sodium Thioborate Fast Ion Conductor: Na3 B5 S9.

We report a new sodium fast-ion conductor, Na3 B5 S9 , that exhibits a high Na ion total conductivity of 0.80 mS cm-1 (sintered pellet; cold-pressed pellet=0.21 mS cm-1 ). The structure consists of corner-sharing B10 S20 supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well-distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X-ray diffraction and powder synchrotron X-ray diffraction at variable temperatures, solid-state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na-ion mobility (predicted conductivity: 0.96 mS cm-1 ) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice-and existence of well-connected Na ion migration pathways formed via face-sharing polyhedra-in dictating Na ion diffusion.

A New Sodium Thioborate Fast Ion Conductor: Na3B5S9

AbstractWe report a new sodium fast‐ion conductor, Na3B5S9, that exhibits a high Na ion total conductivity of 0.80 mS cm−1 (sintered pellet; cold‐pressed pellet=0.21 mS cm−1). The structure consists of corner‐sharing B10S20 supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well‐distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X‐ray diffraction and powder synchrotron X‐ray diffraction at variable temperatures, solid‐state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na‐ion mobility (predicted conductivity: 0.96 mS cm−1) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice—and existence of well‐connected Na ion migration pathways formed via face‐sharing polyhedra—in dictating Na ion diffusion.

New emerging magnetic, optical and photocatalytic properties of Tb doped TiO2 interfaced with CoFe2O4 nanoparticles

The CoFe2O4/TiO2:Tb composite nanoparticles were prepared by a two-stage chemical route. The composites were characterized by using X-Ray Diffraction, Transmission Electron Microscopy, X-ray and UV Photoelectron Spectroscopies, FT-IR, Raman and UV–Vis spectroscopies.There is a polarized spin transfer at the interface between the cobalt ferrite into the TiO2 conduction band. As a result, the magnetic moments of oxygen vacancies in TiO2 becomes (ferro) magnetically ordered. The magnetic moments sublattice of Tb ions may have an either “ferro” or “antifero” coupling depending on the dopant concentration. The magnetic semiconductor intensifies the optical absorption in the visible. There is a band-to-band absorption assisted by single-occupied oxygen vacancies coupled to some local crystal lattice relaxations.The lifetime of the photoexcited electrons in the conduction band increases due to their coupling with magnetically ordered interface transferred states. Also, the trapping of electrons into multiplet states of Tb3+ reduces the recombination rate. The photocatalytic efficiency of the magnetically ordered titania increases with respect to bare TiO2. The reactive oxygen species produced at the solid–liquid interface of TiO2 were identified by Electron Spin Resonance coupled with spin-trapping technique. The results were correlated to the presence of the magnetic order inside the titania.

Atomistic investigation of uranium oxycarbide (UCO) phase stability at finite temperatures: DFT+U and AIMD+U approaches

Materials properties of uranium oxycarbide (UCO), a fuel candidate for high temperature gas reactors (HTGRs), are investigated using the Hubbard corrected density functional theory (DFT+ U ) and ab initio molecular dynamics (AIMD+ U ). To accurately describe UCO systems within the supercell approach, we have evaluated the structural disorder of the ion sublattice within the special quasirandom structures (SQS) approach. The ground-state of UC x O 2-x and UC 1-x O x systems was found by examination of the electronic configuration, the occupation matrix and the Hubbard U parameter. We obtained the electronic properties, lattice structure, formation enthalpy and free energy of mixing of the stoichiometric UC x O 2-x and UC 1-x O x phases. Subsequently, we have determined the preferential phase of UCO (UC x O 2-x or UC 1-x O x ) for low carbon and oxygen concentrations, respectively. In particular, UC x O 2-x was found stable for carbon content lower than 50%, with carbon atoms in the first coordination shell out of the perfect fluorite positions, driven by the formation of C 2 groups as in α -UC 2 . Moreover, the analysis of the radial distribution functions shows that structures with C 2 groups remain stable in the range of temperatures from 300 to ∼ 2500 K.

Controlling protein assembly on inorganic crystals through designed protein interfaces.

The ability of proteins and other macromolecules to interact with inorganic surfaces is critical to biological function. The proteins involved in these interactions are highly charged and often rich in carboxylic acid side chains1-5, but the structures of most protein-inorganic interfaces are unknown. We explored the possibility of systematically designing structured protein-mineral interfaces guided by the example of ice-binding proteins, which present arrays of threonine residues matched to the ice lattice that order clathrate waters into an ice-like structure6. We designed proteins displaying arrays of up to 54 carboxylate residues geometrically matched to the K+ sublattice on muscovite mica (001). At low [K+] individual molecules bind independently to mica in the designed orientations, while at high [K+], the designs form 2D liquid-crystal phases, which accentuate the inherent structural bias in the muscovite lattice to produce protein arrays ordered over tens of millimeters. Incorporation of designed protein-protein interactions preserving the match between the proteins and the K+ lattice led to extended self-assembled structures on mica: designed end-to-end interactions produced micron long single protein-diameter wires, and a designed trimeric interface yielded extensive honeycomb arrays. The nearest neighbor distances in these hexagonal arrays could be set digitally between 7.5 and 15.9 nm with 2.1 nm selectivity by changing the number of repeat units in the monomer. These results demonstrate that protein-inorganic lattice interactions can be systematically programmed and set the stage for designing protein-inorganic hybrid materials.

Griffiths phase in antiferromagnetic CuCr0.95Ti0.05O2

Delafossite compound, CuCrO2, popularly known as transparent conducting oxide, has previously been reported to demonstrate antiferromagnetic ordering of the triangular magnetic lattice below 24 K. We find that mere 5% Ti-substitution at Cr-site, leads to short range magnetic correlations, manifested as non-analytical behaviour of H/M and other anomalies in the low magnetic field dc magnetization, ac magnetic susceptibility, time dependent magnetization, and isothermal remanent magnetization. The ac susceptibility measured at different applied frequencies do not show any frequency dependence, ruling out the glassy magnetic phase. The short-range magnetic correlations are observed over a wide temperature range starting from 180 K and below, until the system orders antiferromagnetically at 22 K. These correlations which are most pronounced at low values of applied magnetic field, get readily suppressed when the fields exceed 0.5 T. Signatures associated with these short-range correlations seem to fit a Griffiths-like phase description. The results of heat capacity measurement with and without magnetic field, provides additional information about the dimensionality of the magnetic interactions. Rietveld refinement of the X-ray diffraction data reveals that the highly anisotropic crystal structure remains unaffected with the substitution. A static disorder driven magnetic inhomogeneity arising in the triangular magnetic sublattice of Cr ions decreases the dimensionality of magnetic interactions, and seems to be the possible origin of this interesting magnetic behaviour.

Synthesis and characterization of electrical features of bismuth manganite and bismuth ferrite: effects of doping in cationic and anionic sublattice: Materials for applications

The electrical, magnetic, and structural features of bismuth manganite (BM), e.g., BiMnO3, and bismuth ferrite (BF), e.g., BiFeO3, are reviewed. Induced multiferroicity and enhanced magnetoelectric coupling are required for various modern device applications. BM and BF were synthesized using standard high-temperature sintering and processes such as sol–gel, hydrothermal, or wet chemical methods combined with annealing. The size and morphology of the nanoscale particles were controlled, although they were usually inhomogeneous. BF exhibits structurally stable antiferromagnetic (AFM) and ferroelectric (FE) phases in wide temperature ranges. Ferromagnetic (FM) order was induced in a thick shell around the AFM core of the nanoscale BF particles, which was attributed to a size effect related to surface strains and disorder. BM exhibited both structurally stable and unstable phases. The BiMnO3, Bi12MnO20, and BiMn2O5 structures are nonferroelectric. The perovskite BiMnO3 form was synthesized under high hydrostatic pressure. FM order occurs in BM at low temperatures. Bi(MnFe)O3 solid solution samples exhibited competition between AFM and FM ordering. Doping can decrease the content of unavoidable secondary phases. Doping in the Bi ion sublattice can stabilize the crystal lattice owing to local strains caused by the difference in ionic radius between Bi and the dopant. Doping in the Fe and Mn sublattices affects the electrical features. The main achievement of substitution with tetra- and pentavalent ions is compensation of the oxygen vacancies. In turn, leakage current suppression enables switching of FE domains and polarization of the samples. A significant enhancement of magnetoelectric coupling was observed in composites formed from BF and other FE materials. The leakage currents can be diminished when an insulator polymer matrix blocks percolation. The potential applicability is related to enhanced magnetoelectric coupling. The constructed devices meet the size effect limitations for FE and FM ordering. Resistive switching suggests possible use in nonvolatile memories and gaseous sensors. The sensors can be used for hydrophones and for photovoltaic and photoluminescence applications, and they can be constructed from multiphase materials. Bulk multiferroic solid solutions, composites, and nanoheterostructures have already been tested for use in sensors, transducers, and read/write devices for technical purposes.

Magnetic, superconducting and electron-boson properties of GdO(F)FeAs oxypnictides

We performed comprehensive studies of nearly optimal fluorine-substituted GdO1−xFx FeAs oxypnictide superconductors with TC=48−53K. Specific heat measurements revealed a sharp peak at T=3.5K that shifts to lower temperatures with magnetic field increase. This peak corresponds to an antiferromagnetic ordering in Gd3+ ion sublattice and may indicate coexistence between superconducting and magnetic orderings. Andreev transport through artificially made constriction demonstrated two channels for the carriers from the band(s) with the large superconducting gap as well as from those with the small gap. As expected, the presence of a transport channel with the bands mixing (ΔL+ΔS) was not detected. Using intrinsic multiple Andreev reflections effect (IMARE) spectroscopy, we determined two superconducting gaps, ΔS≈2.7meV, and ΔL≈11.6meV. The reproducible fine structure in the dI(V)/dV spectra of the Andreev contacts (satellites of the main subharmonic gap structure for ΔL) was interpreted as caused by a resonant emission of bosons with the energy ε0=12−15meV≈ΔL+ΔS during the process of multiple Andreev reflections (MAR) for normal carriers in ΔL-band(s) transport channel.

Anisotropic Proton and Oxygen Ion Conductivity in Epitaxial Ba2In2O5 Thin Films

Solid oxide oxygen ion and proton conductors are a highly important class of materials for renewable energy conversion devices like solid oxide fuel cells. Ba2In2O5 (BIO) exhibits both oxygen ion and proton conduction, in dry and humid environment, respectively. In dry environment, the brownmillerite crystal structure of BIO exhibits an ordered oxygen ion sublattice, which has been speculated to result in anisotropic oxygen ion conduction. The hydrated structure of BIO, however, resembles a perovskite and the protons in it were predicted to be ordered in layers. To complement the significant theoretical and experimental efforts recently reported on the potentially anisotropic conductive properties in BIO, we measure here the proton and oxygen ion conductivity along different crystallographic directions. Using epitaxial thin films with different crystallographic orientations the charge transport for both charge carriers is shown to be anisotropic. The anisotropy of the oxygen ion conduction can indeed be explained through the layered structure of the oxygen sublattice in brownmillerite BIO. The anisotropic proton conduction however, further supports the suggested ordering of the protonic defects in the material. The differences in proton conduction along different crystallographic directions attributed to proton ordering in BIO are of a similar extent as those observed along different crystallographic directions in materials where proton ordering is not present but where protons find preferential conduction pathways through chain-like or layered structures.

Activation energy of ion motion in the nanodimensional lattice of LaF3 superionic conductor

Quantum chemistry calculations of the intracrystalline potential relief in the nanolattice of LaF3 superionic crystal that contains 1200 ions and measures 3.5 × 2.0 × 2.2 nm along the x, y, and z axis, respectively, have been performed. Using the MOPAC 2012 program package, the potential relief profile has been simulated in the central part of the nanolattice for an elementary act of disordering in the lowest melting sublattice of F1 ions. It has been found that the height Em of barriers that prevent the motion of F1 in the dielectric phase of LaF3 crystal equals 0.37 eV and decreases to 0.15 eV in the superionic state. In addition, activation energy Ea of F1 sublattice disordering in the dielectric and superionic states is equal to 0.16 and 0.04 eV, respectively. The profiles of the potential relief calculated on the xy and xz faces of the LaF3 3D nanolattice for the case when an F1 ion moves along the x crystal axis in the dielectric state are presented. The corresponding energy barriers are 1.5–2.0 times lower than those at the center of the LaF3 nanlattice.

Efficient multicolor tunability of ultrasmall ternary-doped LaF3 nanoparticles: energy conversion and magnetic behavior.

Luminescence-tunable multicolored LaF3:xCe3+,xGd3+,yEu3+ (x = 5; y = 1, 5, 10, and 15 mol%) nanoparticles have been synthesized via a low cost polyol method. Powder X-ray diffraction and high-resolution transmission electron microscopy studies confirm the hexagonal phase of the LaF3:xCe3+,xGd3+,yEu3+ nanophosphors with average sizes (oval shape) ranging from 5 to 7 nm. Energy-dispersive X-ray spectroscopy analyses show the uniform distribution of Ce3+, Gd3+, and Eu3+ dopants in the LaF3 host matrix. The photoluminescence spectra and electron paramagnetic resonance measurements guarantee the presence of Eu2+, corroborated through DC susceptibility measurements of the samples displaying paramagnetic behavior at 300 K, whereas weak ferromagnetic ordering is shown at 2 K. The non-radiative energy transfer processes from the 4f(2F5/2) → 5d state (Ce3+) to the intraconfigurational 4f excited levels of rare earth ions and simultaneous emissions in the visible region from the 4f65d1 (Eu2+) and 5D0 (Eu3+) emitting levels, leading to overlapped broad and narrow emission bands, have been proclaimed. The energy transfer mechanism proposes involvement of the Gd3+ ion sub-lattice as the bridge and finally trapping by Eu2+/3+, upon excitation of the Ce3+ ion. The calculation of experimental intensity parameters (Ω2,4) has been discussed and the highest emission quantum efficiency (η = 85%) of the Eu3+ ion for the y = 10 mol% sample is reported. The advantageous existence of the Eu2+/Eu3+ ratio along with variously doped nanomaterials described in this work, results in tunable emission color in the blue-white-red regions, highlighting the potential application of the samples in solid-state lighting devices, scintillation devices, and multiplex detection.

Incommensurate short-range multipolar order parameter of phase II in Ce3Pd20Si6

The clathrate compound Ce3Pd20Si6 is a heavy-fermion metal that exhibits magnetically hidden order at low temperatures. Reputedly, this exotic type of magnetic ground state, known as "phase II", could be associated with the ordering of Ce 4f quadrupolar moments. In contrast to conventional (dipolar) order, it has vanishing Bragg intensity in zero magnetic field and, as a result, has escaped direct observation by neutron scattering until now. Here we report the observation of diffuse magnetic neutron scattering induced by an application of magnetic field along either the [110] or the [001] direction within phase II. The broad elastic magnetic signal that surrounds the (111) structural Bragg peak can be attributed to a short-range G-type antiferromagnetic arrangement of field-induced dipoles modulated by the underlying multipolar order on the simple-cubic sublattice of Ce ions occupying the 8c Wyckoff site. In addition, for magnetic fields applied along the [001] direction, the diffuse magnetic peaks in Ce3Pd20Si6 become incommensurate, suggesting a more complex modulated structure of the underlying multipolar order that can be continuously tuned by a magnetic field.

UV and IR emission intensity in ZnO films, nanorods, and bulk single crystals doped with Er and additionally introduced impurities

For ZnO films, nanorods, and bulk single crystals doped with Er+ ions, it is shown that the effect of codopants introduced into the cation and ion sublattices and the observation of a high-intensity emission band at the wavelength λmax = 1535 nm are defined by the local environment of the Er+ ion. Doping of the films and single crystals with Er+ ions by diffusion brings about an infrared (IR) emission band with a low intensity because of an inadequate concentration of impurity ions. The emission intensity of this band can be raised by introducing additional Ag, Au, or N+ impurities into the ZnO films. The UV-emission intensity of the Er-doped films and single crystals at λmax = 368–372 nm is identical to that of the undoped films. ZnO nanorods doped with Er only or together with Al or Ga codopants exhibit only one IR band (at λmax = 1535 nm), whose intensity decreases upon the introduction of codopants. Doping of the nanorods with the N+ gaseous impurity during growth (930 < T < 960°C) and then with the Er+ impurity by diffusion does not yield a substantial increase in the IR-emission intensity compared to the that of the corresponding band for nanorods not doped with the N+ impurity. In the Er-doped nanorods, whose photoluminescence spectra exhibit a high-intensity band at λmax = 1535 nm, the UV emission band at λmax = 372 nm is practically lacking.

New series of triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) with framework structures and mobile silver ion sublattices

Triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg3In(MoO4)5 type were synthesized and single crystals of AgMg3R(MoO4)5 (R=Cr, Fe) were grown. In their structures, the MoO4 tetrahedra, pairs and trimers of edge-shared (Mg, R)O6 octahedra are connected by common vertices to form a 3D framework. Large framework cavities involve Ag+ cations disordered on three nearby positions with CN=3+1 or 4+1. Alternating (Mg, R)O6 octahedra and MoO4 tetrahedra in the framework form quadrangular windows penetrable for Ag+ at elevated temperatures. Above 653–673K, the newly obtained molybdates demonstrate abrupt reduction of the activation energy to 0.4–0.6eV. At 773K, AgMg3Al(MoO4)5 shows electric conductivity 2.5·10−2S/cm and Ea=0.39eV compatible with characteristics of the best ionic conductors of the NASICON type.

Crystal structure and low-temperature physical properties of CePd0.427Sn2

The ternary stannide CePd0.427Sn2 was investigated by means of powder and single crystal X-ray diffraction, magnetic, electrical transport and heat capacity measurements. Phase stability studies showed that CePd0.427Sn2 forms within a linear composition range of the stannide CePd1−xSn2 set by 0.57 ≤ x ≤ 0.67. The compound was found to crystallize with a defect CeNiSi2-type structure, space group Cmcm, a = 4.558(3) Å, b = 17.410(11) Å, c = 4.4849(17) Å (single-crystal data). Physical measurements revealed that CePd0.427Sn2 is a Curie–Weiss paramagnet due to the sublattice of trivalent Ce ions. The compound exhibits weak Kondo effect and probably orders antiferromagnetically below about 1.5 K.

Magnetic and Mössbauer characterization of the magnetic properties of single-crystalline sub-micron sized Bi2Fe4O9 cubes

Magnetic and Mössbauer characterization of single crystalline, sub-micron sized Bi2Fe4O9 cubes has been performed using SQUID magnetometry and transmission Mössbauer spectroscopy in the temperature range of 4.2 K ≤ T ≤ 300 K. A broad magnetic phase transition from the paramagnetic to the anti-ferromagnetic state is observed below 250 K, with the Mössbauer spectra exhibiting a superposition of magnetic, collapsed and quadrupolar spectra in the transition region of 200 K < T < 245 K. Room temperature Mössbauer spectra obtained in transmission geometry are identical to those recorded in back-scattering geometry via conversion electron Mössbauer spectroscopy, indicating the absence of strain at the surface. A small hysteresis loop is observed in SQUID measurements at 5 K, attributable to the presence of weak-ferromagnetism arising from the canting of Fe3+ ion sublattices in the antiferromagnetic matrix.