Table 2. Selected Bond Lengths (Å) and Angles (º) Bond Distances Cu N2 1.9219(17) Cu N4 1.9414(19) Cu O 1.9756(14) Cu N3 2.0112(17) S C14 1.643(2) N1 C7 1.334(2) N1 N2 1.366(2) N2 C8 1.282(3) N3 C13 1.328(3) N3 C9 1.365(3) N4 C14 1.161(3) O C7 1.283(2) C1 C6 1.395(3) C1 C2 1.396(3) C1 C7 1.486(3) C2 C3 1.384(3) C3 C4 1.394(3) C4 C5 1.379(3) C5 C6 1.381(3) C8 C9 1.463(3) C9 C10 1.379(3) C10 C11 1.390(3) C11 C12 1.385(3) C12 C13 1.384(3) C14 N4 1.161(3) Bond Angles N2 Cu N4 160.77(7) N2 Cu O 79.51(6) N4 Cu O 98.24(7) N2 Cu N3 80.70(7) N4 Cu N3 99.81(7) O Cu N3 160.12(6) C7 N1 N2 107.45(16) C8 N2 N1 123.55(17) C8 N2 Cu 118.46(14) N1 N2 Cu 117.91(12) C13 N3 C9 118.89(18) C13 N3 Cu 128.68(15) C9 N3 Cu 112.43(13) C14 N4 Cu 158.64(17) C7 O Cu 110.08(12) O C7 N1 125.00(18) O C7 C1 119.21(17) N1 C7 C1 115.79(18) N2 C8 C9 114.52(19) N3 C9 C10 121.82(19) N3 C9 C8 113.82(18) C10 C9 C8 124.4(2) C9 C10 C11 118.6(2) N3 C13 C12 122.5(2) N4 C14 S 178.00(19) Figure 1. Clinographic projection of the complex compound References [1] Ratten R. S., Robson R. Angew. Chem. Int. Ed. Engl. 37 (1998) 1460. [2] Mangia, A., Nardelli, M., Pelizzi, C. & Pelizzi, G. Acta Cryst. B30 (1974) 17 [3] Mangia A., Nardelli M., & Pelizzi G. Acta Cryst. B30 (1974) 487 [4] Affan M.,Shamsuddin M., Sukeri M., Yusof M. and Yamin B. Acta Cryst. E60 (2004) m126 109
Magnetic Phase Transition in Synthetic Cobalt-Olivine A.P. Sazonov 1* , M. Meven 2 , V. Hutanu 1 , G. Heger 1 , M. Merz 1 , V.V. Sikolenko 3 1 Institute of Cristallography, RWTH Aachen, D-52056 Aachen, Germany 2 ZWE FRM-II, TU Munich, D-85747 Garching, Germany 3 BENSC, HMI, D-14109 Berlin, Germany *E-mail: andrew.sazonov@frm2.tum.de Olivine-type silicates, M 2 SiO 4 (M – divalent cation), are a major and important component of the upper Earth’s mantle. Therefore, the properties of these materials are of considerable interest in physics, geology and crystal chemistry. Olivine compounds are used as an important composition in some refractory materials, additives in cement concrete, acid-resistant containers, ceramic pigments, etc. Well known examples of natural olivine-type silicates are fayalite (Fe 2 SiO 4 , with paramagnetic Fe 2+ ions) and forsterite (Mg 2 SiO 4 , with diamagnetic Mg 2+ ions). There are also a few natural members with another transition (Mn, Ni) or alkaline-earth (Ca) metal ions and their mixtures, e.g. tephroite (Mn 2 SiO 4 ), kirschsteinite (CaFeSiO 4 ), etc. A remarkable feature of the orthorhombic olivine-type structure (space group Pnma, no. 62 [1]) consists in two crystallographically non-equivalent M positions. Moreover, these systems are interesting due to the peculiarities of their magnetic structures. The magnetic properties of olivine compounds are quite complex and depend on type of M cation. Synthetic Co 2 SiO 4 also crystallizes in the olivine-type structure. An antiferromagnetic phase transition occurs in this compound. However, the magnetic properties of Co 2 SiO 4 were not yet well understood. Therefore, in order to determine the nature of magnetism in this system we have performed both X-ray and neutron diffraction studies as well as magnetization measurements of cobalt-olivine. A large Co 2 SiO 4 single crystal (length ~ 1.5 cm, diameter ~ 0.5 cm) was grown by the zone melting method using a mirror furnace (Inst. of Cryst., RWTH, Aachen). The phase purity was checked using the high resolution X-ray powder diffraction (MILIDI, Inst. of Cryst., RWTH, Aachen) in the temperature range from 19 to 300 K with Cu Kα radiation. The unpolarized neutron diffraction measurements were done using the single crystal diffractometer HEiDi [2] at the hot source of the FRM-II (TU Munich, Germany). Data were collected at 2 K, 55 K and 300 K with wavelength of 0.55 Å up to about sinΘ/λ ≈ 1.1 Å -1 . We have measured 3021 reflections all together with 1223 unique reflections (891 reflections with I > 3σ(I)) at 2 K. Likewise, 2232 reflections all together with 1390 unique reflections (1026 reflections with I > 3σ(I)) were collected at 55 K. At room temperature we have measured 2357 reflections with 1465 unique reflections (1092 reflections with I > 3σ(I)). Temperature stability was better than 0.1 K. The neutron diffraction data were analyzed with the Rietveld method using the FullProf program [3]. The dc magnetization measurements were performed using a Quantum Design MPMS-5 SQUID magnetometer (HMI, Berlin). The temperature dependencies of the magnetization M(T) were measured on warming from 4 to 300 K in a field of 5 T. As was already pointed out, Co 2 SiO 4 have an olivine-type orthorhombic crystal structure with the space group Pnma in which four formula units are contained in the unit cell (figure 1). The silicon atoms are coordinated with the four oxygen atoms to form SiO 4 tetrahedra. The cobalt atoms are surrounded by the six oxygen atoms and form CoO 6 octahedra. There are two crystallographically non-equivalent Co sites, where Co I (4a) ions are sites of inversion symmetry (the smaller and more distorted sites), and Co II (4c) ions are in the plane of mirror symmetry (the lager and less distorted sites). Preliminary studies of the sample at/below room temperature were carried out using X-ray diffraction, and the crystal structure is confirmed to be orthorhombic. The results indicate that the general trend of the thermal expansion appears to be normal; the unit cell parameters and the cell volume were found to gradually increase with temperature (figure 2). a (A) 10.31 10.30 10.29 10.28 b (A) 6.00 5.99 c (A) 4.785 4.780 Figure 1. A schematic representation of Co 2 SiO 4 crystal structure V (A 3 ) 4.775 296 295 294 0 50 100 150 200 250 300 T (K) Figure 2. Temperature dependency of the lattice parameters and cell volume of Co 2 SiO 4 According to experimental data, an antiferromagnetic phase transition occurs in this compound at T N ≈ 50 K (figures 3 and 4 and ref. [4]). On the other hand, no significant anomalies were observed in the cell parameters at temperatures near T N . The investigation of any subtle changes should be performed with smaller temperature steps, but this is outside the scope of the present work. 110
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XXIII ΠΑΝΕΛΛΗΝΙΟ ΣΥΝΕ
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Κοιτώντας τα πρακτ
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ΕΠΙΤΡΟΠΕΣ Οργανωτι
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ΠΡΟΓΡΑΜΜΑ ΣΥΝΕΔΡΙΟ
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21. Οργανικά τρανζίσ
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15:30 15:45 16:00 16:15 16:30 16:45
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41. Modeling and quantitative phase
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Ανοιχτή Συνεδρία «
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«NανοΥλικά και Νανο
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New materials and MOS device concep
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Reliability Characteristics of Rare
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Ο λόγος των ταχυτήτ
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Thus the mean R In-In is expected t
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FIG 1. Schematic representation of
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με 0.80 eV στη διεπιφά
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Εντοπισµός Φορέων
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Παρασκευή και Xαρακ
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Electrical Spin Injection from Fe i
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Electrical Spin Injection of Spin-P
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References [1] CH Lee, J. Meteer, V
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Σχήμα 1: Φωτογραφία
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SEM Image Layout Simulation Εικ
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Μελέτη Ατελειών Σε
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Facet-Stress-Driven Ordering in SiG
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νανοκρυσταλλίτης (a
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Σχήµα 1. Εικόνες περ
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Σχήµα 1. Εικόνες περ
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Οι δομές που αναπτύ
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Raman Intensity (10 -50 cm 3 ) 1,2
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Μελέτη της Επίδρασ
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Annealing Induced Dissociation of N
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`Εναπόθεση με Παλμι
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Μελέτη της Χημείας
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Ανάπτυξη Νέων Μεσο
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Application of Thermal Quadrupoles
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Στοχαστική προσομο
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Νανοτραχύτητα κατά
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Ευαισθησία και Δια
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AP-PH (a.u.) 0.4 0.3 0.2 0.1 0.0 0
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Synthesis of Polymer Brushes onto I
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Conformational Properties of Dendri
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Structure and Dynamics of Branched
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∆οµή και ∆υναµική
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Επίδραση της Τοπολ
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(α) (β) Σχήμα 2: (α) Απε
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Figure 3. Generation 4 PAMAM-H 2 O
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Από όλα τα παραπάνω
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Το PHEGMA είναι άμορφο
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PS HAuCl 4 P2VP Ion loading PSP2VP
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The nonlinear optical response of A
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νανοσωµατίδια. Όπω
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Bioactive Glass/Nanodiamonds system
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Energy Loss Rates of Hot Electrons
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Σύνθεση και Χαρακτ
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μπορεί να ερμηνευτ
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Nανοσυνθέτα Εποξει
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[1] S. Iijima, Nature 354, 56 (1991
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Figure 3: GCMC calculations for und
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μερών, εμφανίζοντα
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1.0 Reflectance 1.1 1.0 0.9 0.8 0.7
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στο συντελεστή διέ
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¿ÔÖØÑÒØÓÐØÖÐÒÒÖÒ¸
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Συναπόθεση Cr - Ni σε
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Investigation of the Structural, Mo
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Modification of Perlite Cementitiou
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Templated Sol-Gel Synthesis Of TiO
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Παρασκευή Υμενίων
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Preparation of YSZ Solid Electrolyt
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Σύνθεση, Ανισοτροπ
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Μελέτη ανθρώπινων
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Local Coordination of Zn and Fe in
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Επίδραση της Προσθ
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Αλκαλική Σύνθεση κ
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The Influence of Thermal Aging on t
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Modeling and quantitative phase ana
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Συμβολή στη Συντήρ
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Fabrication and Characterization of
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∆ιερεύνηση δυνατό
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Συγκριτική αξιολόγ
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Ηλεκτρομαγνητική Α
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Φασματοσκοπική Μελ
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Thermal and Electrical Properties o
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Structure, Mechanical, and Optoelec
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Designing Nanoporous Materials for
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This program was developed to serve
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Νέα Αυτό-οργανούμε
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A Physical Model to Interpret the E
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FIR study of Ag x (As 33 S 33 Se 33
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Mελέτη Μεικτών Γυαλ
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The Structural Role of Fe and Zn in
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ΕΥΡΕΤΗΡΙΟ ΣΥΓΓΡΑΦΕ
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Κομπίτσας Μ…………
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ΕΥΡΕΤΗΡΙΟ ΣΥΓΓΡΑΦΕ
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W Watson I.M………………4 Weg
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