The magnetic structure of the intermetallic compound ErGa has been determined using high-resolution neutron powder diffraction. This compound crystallizes in the orthorhombic (Cmcm, No. 63) CrB-type structure and orders ferromagnetically at 32 (2) K, with the Er moments initially aligned along the b axis. Upon cooling below 16 K, the Er magnetic moments cant away from the b axis towards the c axis. At 3 K, the Er moment is 8.7 (3) μB and the Er magnetic moments point in the direction 31 (3)° away from the crystallographic b axis, within the bc plane. 166Er Mössbauer spectroscopy work supports this structure and shows clear signals of the spin-reorientation in both the magnetic and electric quadrupole hyperfine interactions.

Here, we report the growth of (Sr, Ca) Nd2Fe2O7 single crystals with the Ruddlesden–Popper structure using an optical floating-zone method. A significantly anisotropic magneto-dielectric effect (MD), ab-plane and c-axial MD coefficients reaching −12.3% and −8.4% measured at 103 Hz in a 1 T magnetic field, can be obtained in a SrNd2Fe2O7 crystal at room temperature. The corresponding anisotropic MD ratio can be reached as high as 1.46. With an increase in the Ca concentration, the MD effect decreases dramatically and is eventually completely suppressed in both directions. Analysis of magnetic properties and 57Fe Mössbauer spectra suggests that the anisotropic MD effects in SrNd2Fe2O7 can be attributed to polaronic hopping between two neighboring Fe3+ ions through oxygen vacancies in an anisotropically antiferromagnetic matrix; the disappearance of the MD effect in Ca-doped SrNd2Fe2O7 is a consequence of the suppression of the antiferromagnetism. Our work suggests that the significantly anisotropic MD effect in SrNd2Fe2O7 crystals at room temperature can be used in magneto-dielectric controlled devices.

Murrili, the third meteorite recovered by the Desert Fireball Network, is analyzed using mineralogy, oxygen isotopes, bulk chemistry, physical properties, noble gases, and cosmogenic radionuclides. The modal mineralogy, bulk chemistry, magnetic susceptibility, physical properties, and oxygen isotopes of Murrili point to it being an H5 ordinary chondrite. It is heterogeneously shocked (S2–S5), depending on the method used to determine it, although Murrili is not obviously brecciated in texture. Cosmogenic radionuclides yield a cosmic ray exposure age of 6–8 Ma, and a pre‐atmospheric meteoroid size of 15–20 cm in radius. Murrili’s fall and subsequent month‐long embedment into the salt lake Kati Thanda significantly altered the whole rock, evident in its Mössbauer spectra, and visual inspection of cut sections. Murrili may have experienced minor, but subsequent, impacts after its formation 4475.3 ± 2.3 Ma, which left it heterogeneously shocked.

Energy-efficient and environment-friendly solid-state magnetic refrigeration requires materials with extraordinary magnetocaloric properties. We report the plateau-like magnetocaloric effect activated by tripled magnetic cell in layered intermetallic TbMn2-xCoxSi2 compounds, and the consequent large refrigerant capacity. Substitution of Mn with Co significantly modified the magnetic properties evidenced by two successive ferromagnetic first-order transitions and strong magneto-elasticity as well as significant contraction of the unit cell. Detailed neutron diffraction investigations have established the formation of a tripled magnetic unit cell structure at the temperature range between two magnetic transitions. The overlapping entropy curves near the two transition temperatures results in a plateau-like magnetocaloric effect and enhanced refrigerant capacity. Existence of this special magnetic cell also leads to a variety of interesting physical properties, including a significant drop in resistance and pronounced anomalies in the heat capacity, as well as different responses of the two transition temperatures to an applied magnetic field. The impact of the formation of a tripled magnetic cell on the physical properties is highly unusual for magnetic alloys and merits expanded investigation of this class of magnetic materials to explore for novel applications.

Analysis of inelastic neutron scattering data recorded for the rare earth intermetallic compound TmV2Al20 yields a cubic crystal field Hamiltonian with parameters x = -0.63(1) and W = +0.43(1) K (Lea, Leask & Wolf notation). This result is supported by a strong electron paramagnetic resonance signal that is consistent with magnetic splitting of the first excited (T-5((1))) state. Using this crystal field Hamiltonian, single crystal magnetisation and specific heat data are then interpreted in terms of a model that involves partial Al flux substitution of an approximately 10% depleted Tm "cage" site. (C) 2020 Elsevier B.V. All rights reserved.

Polycrystalline samples of CaLa2FeCoSbO9 and ALa(2)FeNiSbO(9) (A = Ca, Sr, Ba) have been prepared in solid-state reactions and studied by a combination of transmission electron microscopy, magnetometry, X-ray diffraction, neutron diffraction and Massbauer spectroscopy. Diffraction and TEM showed that each shows 1:1 B-site ordering in which Co2+/Ni2+ and Sb5+ tend to occupy two distinct crystallographic sites while Fe3+ is distributed over both sites. While X-ray and neutron diffraction agreed that all four compositions are monophasic with space group P2(1)/n, TEM revealed different levels of compositional inhomogeneity at the subcrystal scale, which, in the case of BaLa2FeNiSbO9, leads to the occurrence of both a P2(1)/n and an I2/m phase. Magnetometry and neutron diffraction show that these perovskites are ferrimagnets with a G-type magnetic structure. Their relatively low magnetisation can be attributed to their inhomogeneity. This work demonstrates the importance of studying the microstructure of complex compositions.

The magnetic structures of Er2Fe2Si2C and Tm2Fe2Si2C (monoclinic Dy2Fe2Si2C-type structure, C2/m space group) have been studied by neutron powder diffraction, complemented by magnetization, specific heat measurements, and Er-166 Mossbauer spectroscopy, over the temperature range 0.5 to 300 K. Their magnetic structures are compared with those of other R2Fe2Si2C compounds. Antiferromagnetic ordering of the rare-earth sublattice is observed below the Neel temperatures of T-N = 4.8(2) K and T-N = 2.6(3) K for Er2Fe2Si2C and Tm2Fe2Si2C, respectively. While Er2Fe2Si2C and Tm2Fe2Si2C have the same crystal structure, they possess different magnetic structures compared with the other R2Fe2Si2C (R = Nd, Gd, Tb, Dy, and Ho) compounds. In particular, two different propagation vectors are observed below the Neel temperatures: k = [1/2, 1/2, 0] (for Er2Fe2Si2C) and k = [0.403(1), 1/2, 0] (for Tm2Fe2Si2C). For both compounds, the difference in propagation vectors is also accompanied by different orientations of the Er and Tm magnetic moments. Although the magnetic structures of Er2Fe2Si2C and Tm2Fe2Si2C differ from those of the other R(2)Fe(2)Si(2)Ccompounds, we have established that the two magnetic structures are closely related to each other. Our experimental and first-principles studies indicate that the evolution of the magnetic structures across the R2Fe2Si2C series is a consequence of the complex interplay between the indirect exchange interaction and crystal field effects.

We have used neutron powder diffraction to demonstrate the existence of long-range antiferromagnetic order of Ising-like Dy moments in the DyCd6 quasicrystal approximant phase. This cubic compound undergoes a slight distortion to a monoclinic cell at low temperatures. The Néel temperature is 18.0(2) K and the magnetic order of the Dy sublattice may be described in the parent cubic Im3¯ structure using a combination of two propagation vectors, k1 = [0 0 0] and k2 = [12 0 12], yielding ‘anti-I’ order. Alternatively, when referred to the monoclinic C2/c cell, the magnetic structure may be described by a single propagation vector: k = [1 0 0].

In this work, the effect of Cu-doping on the structural and magnetic properties of the ErNi3Al9 compound is reported. X-ray diffraction (XRD) and magnetization experiments as a function of temperature and applied magnetic field have been performed on Er(Ni1-xCux)(3+y)Al9-y(x = 0.0, 0.1, 0.8, 0.9, 1.0 and y = 0 or 1) intermetallic compounds. XRD analysis shows that the substitution of Ni by Cu in ErNi3Al9 changes the crystal symmetry from trigonal R32 to tetragonal I4/mmm, even though a clear transition region cannot be established due to the presence of secondary metal phases for intermediate Ni-Cu concentrations. The T-dependence of the magnetic susceptibility shows that the transition temperatures across the series are unaffected by the doping. Moreover, the anisotropic magnetic responses of the MvsT curves measured in the ab-plane and along the c-axis for the series end members may be indicative of strong crystalline electric field (CEF) effects. In fact, we suggest a crystal electric field (CEF)-driven effect due to the different point symmetries for those members. By applying an anisotropic spin model we are able to extract the crystal field parameters, reproduce the macroscopic data and compare these to the previously reported experimental values for ErCu4Al8. Finally, our set of data show clearly that the phase transition is more evident in the X-ray and crystal field effects than in the T-dependent magnetization. (C) 2019 Elsevier B.V. All rights reserved.

EFEK 57 Fe DAN 119 Sn MOSSBAUER PADA SENYAWA RFe 6 Sn 6 (R=Y, Gd - Lu) . Telah digunakan efek 57 Fe dan 119 Sn Mossbauer untuk mempelajari sifat - sifat magnetik senyawa Rl7e6Sn6 (R=Y, Gd-Lu). Semua senyawa memiliki medan magnetik superhalus pada inti 57 Fe sebesar ~19,5 T pada suhu 295K dan kuadrupol spliting positif. Hasil eksperimen 119 Sn Mossbauer menunjukkan bahwa hanya 1/3 posisi Sn yang menstransfer momen magnetik dari Fe tetangga terdekat, sedangkan 2/3 posisi Sn memiliki tetangga terdekat atom - atom Fe yang arah momen magnetiknya antiparalel sehingga tidak menstransfer medan magnetik superhalus.

Fil: Betancourth Giraldo, Diana Maria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Cuyo; Argentina. Comision Nacional de Energia Atomica. Gerencia del Area de Energia Nuclear. Instituto Balseiro; Argentina. Comision Nacional de Energia Atomica. Centro Atomico Bariloche; Argentina

Earlier Mössbauer investigations of rare earth chromates RCrO4 with R = Gd and Tm were interpreted in terms of a superposition of two sub-spectra (approx. 4:1 area ratio), despite there being only a single crystallographic R(4a) site. In addition, the magnetic transitions exhibited first-order character, which is contrary to bulk magnetic measurements. However, new 161Dy and 166Er Mössbauer data presented here for DyCrO4 and ErCrO4 show the expected single rare earth site in both cases and a conventional second order behaviour for ErCrO4.

R. A. Susilo,1,* X. Rocquefelte,2,† J. M. Cadogan,1 E. Bruyer,2 W. Lafargue-Dit-Hauret,2,3 W. D. Hutchison,1 M. Avdeev,4,5 D. H. Ryan,6 T. Namiki,7 and S. J. Campbell1 1School of Science, UNSW Canberra at the Australian Defence Force Academy, Canberra BC 2610, Australia 2Université de Rennes, ENSCR, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) UMR 6226, F-35000 Rennes, France 3Physique Théorique des Matériaux, CESAM, Université de Liège, B-4000 Sart Tilman, Belgium 4Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia 5School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia 6Department of Physics, McGill University, Montreal, Québec H3A 2T8, Canada 7Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama 930-8555, Japan

We report detailed investigations on the structural, thermal and magnetic properties of Y2Fe2Si2C over the temperature range 2-300 K using x-ray diffraction, specific heat, Fe-57 Mossbauer spectroscopy and first-principles calculations. Low temperature measurements show no pronounced anomalies which might signal magnetic ordering of the Fe sublattice at low temperature. Analyses of the specific heat data of Y2Fe2Si2C reveal the presence of a localised Einstein mode, suggesting the importance of an optical contribution to the phonon spectrum of Y2Fe2Si2C. Based on electronic structure calculations, we found a low density of states of the Fe 3d bands at the Fermi level. The corresponding density of states are below the Stoner criterion, thus indicating a non-magnetic state of the Fe atoms in Y2Fe2Si2C, in agreement with the experimental findings. (C) 2018 Elsevier B.V. All rights reserved.

We report measurements of the temperature dependent specific heat and magnetic susceptibility in single crystals of the series of intermetallic compounds Tb1-xYxRhIn5 (nominal concentrations x = 0.0, 0.15, 0.3, 0.4, 0.5, 0.7). A mean field approximation to simulate the macroscopic properties along the series has been used. Neutron diffraction data in powdered samples of Tb(0.5)Y(0.4)Rhln(5) and Tb0.6La0.4RhIn5 reveal antiferromagnetic (AFM) propagation vector (k) over right arrow =[1/2 0 1/2] with the magnetic moments oriented along the tetragonal c axis or canted from this axis, respectively for Y and La-substitutions. Considering both the simulations of the magnetic exchange and neutron diffraction data, we discuss the role of combined effects of crystalline electric field (CEF) perturbations and dilution in the evolution of magnetic properties with Y and La contents. In particular, we found negligible variations of the B-n(m) parameters along the Y series. The decrease of TN with x is fully dominated by magnetic dilution effects.

In the present study, the effect of stress-relaxation treatment (Tstress-relaxation < T-glass transition) on the magnetic texture, nanomechanical properties, and variation of free-volume in FeSiBNb amorphous alloy was investigated using Mossbauer spectroscopy, nanoindentation, dynamic mechanical analysis (DMA), and positron annihilation lifetime spectroscopy (PALS) techniques. It was shown that stress-relaxation treatment slightly improved the magnetic texture by 6% at T << T-g due to small-scale displacement of atoms whereas the magnetic texture was deteriorated due to thermal treatment at temperatures around the glass transition point (large-scale displacement of atoms). According to nanoindentation results, the hardness (H) and reduced modulus (E-r) of the amorphous ribbon increased by 15% and 13%, respectively, after stress-relaxation treatment at 716 K for 5 min. Increasing the stress-relaxation time from 5 min to 60 min at 716 K resulted in decreases in the hardness and reduced modulus which are attributed to the increase of free-volume defects (increase of tau(2) lifetime measured by PALS). Transmission electron microscopy (TEM) showed the formation of extremely fine embryos of alpha-Fe (3-5 nm in size) after stress-relaxation treatment. (C) 2018 Elsevier B.V. All rights reserved.

A polycrystalline sample of SrLa2FeCoSbO9 has been prepared in a solid-state reaction and studied by a combination of electron microscopy, magnetometry, Mössbauer spectroscopy, X-ray diffraction, and neutron diffraction. The compound adopts a monoclinic (space group P21/ n; a = 5.6218(6), b = 5.6221(6), c = 7.9440(8) Å, β = 90.050(7)° at 300 K) perovskite-like crystal structure with two crystallographically distinct six-coordinate sites. One of these sites is occupied by 2/3 Co2+, 1/3 Fe3+ and the other by 2/3 Sb5+, 1/3 Fe3+. This pattern of cation ordering results in a transition to a ferrimagnetic phase at 215 K. The magnetic moments on nearest-neighbor, six-coordinate cations align in an antiparallel manner, and the presence of diamagnetic Sb5+ on only one of the two sites results in a nonzero remanent magnetization of ∼1 μB per formula unit at 5 K.

We report measurements of the temperature dependence specific heat, magnetic susceptibility in single crystals of the series of intermetallic compounds Tb_1-xY_xRhIn_5 (nominal concentrations x= 0.15, 0.30, 0.40, 0.50 and 0.70). A mean field approximation to simulate the macroscopic properties along the series has been used. Neutron diffraction data in powdered sample of nominal concentration Tb_0.6Y_0.4RhIn_5 reveal AFM propagation vector k=[1/2 0 1/2] with the magnetic moments oriented close to the tetragonal c axis. We discuss the role of combined effects of crystalline electric field (CEF) perturbations and dilution in the magnetic properties evolution with Y content. In particular, we suggest that changes in the Tb-In first neighbors distances, i.e. the TbIn_3 cuboctahedra distortion, are responsible for changes in the Tb crystalline potential and the possible reorientation of Tb magnetic moments for x>0.4. This reflects non negligible variations of the B^m_n crystal field parameters and the energy levels splitting with x.

The Lynch 001 meteorite was found in the Nullarbor Plain region of Western Australia in 1977. This meteorite is classified as an ordinary chondrite of the petrologic group L5/6 that has undergone ‘minor to moderate’ terrestrial weathering. Here, we characterize the Fe-bearing phases in this chondrite using 57Fe Mössbauer spectroscopy carried out over the temperature range 13 K to room temperature (295 K). The paramagnetic doublets of olivine, pyroxene and a superparamagnetic ferric phase dominate the room temperature Mössbauer spectrum. On the basis of the room temperature quadrupole splitting of the olivine component, we estimate its composition to be Fa 30(5). Besides the paramagnetic ferric component, accounting for ∼15 % of the spectral area at room temperature, magnetically ordered ferric phases were also detected. The total relative proportion of the Fe 3+ components allows us to estimate the terrestrial age of Lynch 001 to be 6,500 ± 1,500 yr, consistent with the value of 6,700 ± 1,300 yr determined by 14C dating.