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1.
Furrer A Strässle T Embs JP Juranyi F Pomjakushin V Schneider M Krämer KW 《Physical review letters》2011,107(11):115502
We introduce a novel method for local structure determination with a spatial resolution of the order of 0.01 ?. It can be applied to materials containing clusters of exchange-coupled magnetic atoms. We use neutron spectroscopy to probe the energies of the cluster excitations which are determined by the interatomic coupling strength J. Since for most materials J is related to the interatomic distance R through a linear relation dJ/dR=α (for dR/R?1), we can directly derive the local distance R from the observed excitation energies. This is exemplified for the mixed one-dimensional paramagnetic compound CsMn(x)Mg(1-x)Br3 (x=0.05,0.10) containing manganese dimers oriented along the hexagonal c axis. Surprisingly, the resulting Mn-Mn distances R do not vary continuously with increasing internal pressure but lock in at some discrete values. 相似文献
2.
V. G. Grebinnik V. N. Duginov V. A. Zhukov S. Kapusta A. B. Lazarev V. G. Olshevsky V. Y. Pomjakushin S. N. Shilov D. T. Bezhitadze I. I. Gurevich B. F. Kirillov E. P. Krasnoperov B. A. Nikolsky A. V. Pirogov A. N. Ponomarev V. A. Suetin G. F. Tavadze I. P. Borovinskaya M. D. Nersesyan A. G. Peresada Y. F. Eltzev V. R. Karasik O. E. Omelyanovsky 《Hyperfine Interactions》1990,61(1-4):1093-1096
We report the results of μSR investigations of the ceramic samples La2-xSrxCuO4-σ (x=0.1, 0.15, 0.25) and ReBa2Cu3O7-σ (Re=Er, Ho, Y0.5Ho0.5) in the external magnetic field 0–800 Oe. The measurements were performed by the ZFC and FC methods. The irreversibility effects were studied at several temperatures by measuring the mean value and the width of the magnetic field distribution on the muon in the step by step procedure of increasing and subsequent decreasing of the external field. The temperature dependences of the magnetic penetration depth perpendicular to the basal plane λ⊥ were obtained. For the lanthanum sample with 0.15 of Sr its value at the zero temperature is λ⊥ (0)=2400 Å, for Er-Ba-Cu-O λ⊥ (0)=1600 Å. 相似文献
3.
V. G. Grebinnik V. N. Duginov V. A. Zhukov S. Kapusta A. B. Lazarev V. G. Olshevsky V. Y. Pomjakushin S. N. Shilov I. I. Gurevich B. F. Kirillov B. A. Nikolsky A. V. Pirogov A. N. Ponomarev V. A. Suetin I. P. Borovinskaya M. D. Nersesyan A. G. Persada Y. F. Eltzev V. R. Kapasik O. E. Omelyanovski 《Hyperfine Interactions》1990,61(1-4):1085-1088
4.
Malavasi L Mozzati MC Pomjakushin V Tealdi C Azzoni CB Flor G 《The journal of physical chemistry. B》2006,110(35):17414-17419
This paper presents the results of a high-resolution neutron diffraction and magnetometry investigation on the optimally doped (x = 0.3) La(1.4)Sr(0.8)Ca(0.8)Mn(2)O(7) bilayered manganite. In particular, two samples with different oxygen contents have been studied to put in prominence the role of the Mn average valence states at fixed cation concentration. The results show, for the first time, the absence of long-range magnetic order in this optimally doped manganite when the A-site of the structure is doped with equal proportions of isovalent Ca and Sr. This holds for both samples, which present different lattice effects with T, thus suggesting the primary role of cation disorder as the source of the lack of long-range order. The presence, for both samples, of defined insulating- to metallic-like transitions suggests that the transport properties are not linked to the evolution of long-range order and that two-dimensional spin ordering in the layers of the perovskite blocks may be sufficient to "assist" the hole hopping. A possible reason for the suppression of magnetic order induced by the Ca doping is a size effect coupled to the cation size mismatch between the Sr and Ca ions. 相似文献
5.
A. M. Balagurov L. G. Mamsurova I. A. Bobrikov To Thanh Loan V. Yu. Pomjakushin K. S. Pigalskiy N. G. Trusevich A. A. Vishnev 《Journal of Experimental and Theoretical Physics》2012,114(6):1001-1011
The atomic structure of YBa2Cu3O y fine-crystalline HTSC samples with various average crystallite sizes ??D?? ranging from 0.4 to 2 ??m and an oxygen concentration y close to the optimal value for superconductivity (y ?? 6.93) is investigated by the neutron diffraction technique. We have found some effects associated with the redistribution of cations and oxygen atoms and with variations in the positions of atomic layers in the unit cell, which are not observed in macrocrystalline samples. In all probability, these effects appear due to nonequilibrium conditions of synthesis required for obtaining this compound in the fine-crystalline state. The results have made it possible to explain the peculiar physical properties of fine-crystalline YBa2Cu3O y samples (in particular, the coexistence of high superconducting transition temperatures T c and noticeably lower values of magnetization in strong magnetic fields for T < T c ). It is shown that a nanoscale structural inhomogeneity exists in fine-crystalline YBa2Cu3O y samples with the optimal oxygen content and changes the fundamental superconducting parameters, viz., the magnetic field penetration depth and the coherence length. 相似文献
6.
V. G. Grebinnik V. N. Duginov V. A. Zhukov S. Kapusta A. B. Lazarev V. G. Olshevsky V. Yu. Pomjakushin S. N. Shilov I. I. Gurevich B. F. Kirillov E. P. Krasnoperov B. A. Nikolsky A. V. Pirogov A. N. Ponomarev V. A. Suetin A. I. Morozov 《Hyperfine Interactions》1991,63(1-4):241-247
High temperature superconductors HoBa2Cu3O7−δ (T
c
≅93 K), Ho0.5Y0.5Ba2Cu3O7−δ (T
c
≅93 K) and ErBa2Cu3O7−δ (T
c
≅95 K) were investigated by the zero-field μSR-technique. The muon spin depolarisation rate connected with the fluctuation
frequency of rare-earth ion magnetic moments was measured. It was found that the samples with holmium show a fast increase
of the muon spin depolarisation rate at temperatures below 20 K, while in ErBa2Cu3O7−δ the depolarisation rate remains low in the whole temperature region studied (4.2 K-270 K). The sharp difference between the
behaviours of the muon spin depolarisation rate may be explained by the difference between the ground state of Ho3+ and Er3+ ions in the crystalline field of the lattice. 相似文献
7.
V. G. Grebinnik V. N. Duginov V. A. Zhukov S. Kapusta A. B. Lazarev V. G. Olshevsky V. Yu. Pomjakushin S. N. Shilov I. K. Ageenkova A. M. Brjazkalo B. F. Kirillov A. V. Pirogov B. A. Nikolsky A. N. Ponomarev V. N. Sumarokov A. G. Chistov S. Safrata J. Sebek D. Niznansky T. Hanslik H. Sichova 《Hyperfine Interactions》1991,63(1-4):117-122
8.
I.A. Krivosheev V.N. Duginov V.G. Grebinnik K.I. Gritsaj T.N. Mamedov V.N. Nikiforov V.G. Olshevsky V.Yu. Pomjakushin A.N. Ponomarev Yu.D. Seropegin V.A. Zhukov M. Baran H. Szymczak 《Hyperfine Interactions》1997,106(1-4):187-192
We have studied the magnetic spinel (Zn)[Fe2]O4 (T_ N\approx10.5\ K) and the non‐magnetic spinels (Zn)[Al2]O4, (Zn)[Ga2]O4, (Zn)[ZnTi]O4 and (Zn)[ZnSn]O4 , both with surface and decay channel muons. In (Zn)[Fe2]O4 the relaxation rate increases monotonically from room temperature down, typical for a paramagnet. Around 30 K, an additional, stronger damped signal appears which is the signature of short‐range ordered (SRO) regions. Their total volume fraction increases drastically towards T_ N (reaching 75%) and astonishingly, continues to be present also below T_ N where the rest of the material has become long‐range ordered. Longitudinal field μSR proves the SRO to be dynamic. In (Zn)[Al2]O4 and (Zn)[Ga2]O4 muon depolarization is caused solely by 27Al or 69,71Ga nuclear dipoles. In the inverse spinel (Zn)[ZnTi]O4, half of the implanted muons depolarize rapidly (\lambda\approx 3μs-1 at room temperature). This, together with repolarization behavior in longitudinal fields indicates that the muon in (Zn)[ZnTi]O4 undergoes a chemical reaction after implantation forming muonium. The fact that no such muonium formation occurred in another inverse spinel ( (Zn)[ZnSn]O4) means that the presence of muonium is not connected to the inverse structure but rather due to the presence of Ti which offers two d‐electrons to participate in the chemical bonding. Additional evidence for d‐electron participation is provided by 67Zn‐Mössbauer data which indicate unusual electron densities at the 67Zn nuclei only in (Zn)[ZnTi]O4. 相似文献
9.
10.
Aguadero A Escudero MJ Pérez M Alonso JA Pomjakushin V Daza L 《Dalton transactions (Cambridge, England : 2003)》2006,(36):4377-4383
Materials formulated as La(2-x)Sr(x)NiO(4+delta) (0 相似文献