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A 57Fe M?ssbauer Study Of Local Structure And Spin Arrangements In Antiferromagnetic NaFeAs  [PDF]
Igor Presniakov,Igor Morozov,Alexey Sobolev,Mariya Roslova,Alexander Boltalin,Vladimir Son,Olga Volkova,Alexander Vasiliev
Physics , 2012, DOI: 10.1063/1.4759469
Abstract: Detailed 57Fe M\"ossbauer spectroscopy measurements on superconducting NaFeAs powder crystals have been performed. The 57Fe spectra recorded in the paramagnetic temperature range (T > TN \approx 46 +/- 2 K) were discussed supposing Fe2+ ions are located in distorted tetrahedral (FeAs4) polyhedra. Our results reveal that the structural transition (TS \approx 55 K) has a weak effect on the electronic structure of iron atoms while the development of the antiferromagnetic order (T =< TN) induces a redistribution of the charge at 57Fe nuclei. In the low-temperature range, the spectra show a diffuse resonance absorption structure which evidences for the existence of a continuous distribution of hyperfine fields HFe at 57Fe nuclei. The shape of these spectra can be related to the formation of a microdomain structure or phase separation. Analysis of the resulting distributions p(HFe) has shown that the M\"ossbauer spectra give consistent and physically reasonable 57Fe hyperfine parameters over the whole temperature range.


中国物理 B , 1993,
Abstract: 57Fe M?ssbauer spectra have been obtained at room temperature for (NdDy)TiFe11, and at 11 K and room temperature for the corresponding nitrides (NdDy)TiFe11Ny. The magnetic behaviors of Fe atoms at different sites have been studied. We have found a larger increase of the hyperfine fields upon nitrogenation due to the higher nitrogen content in these compounds and got a bigger enhancement of the isomer shift in 8j site because of the nearest nitrogen environment.
Paramagnetic Phase of a Heavy-Fermion Compound, CeFePO, Probed by 57Fe M?ssbauer Spectroscopy  [PDF]
Tetsuro Nakamura,Takashi Yamamoto,Masanori Matoba,Yasuaki Einaga,Yoichi Kamihara
Physics , 2012, DOI: 10.1143/JPSJ.81.064714
Abstract: 57Fe M\"{o}ssbauer spectroscopy was applied to an iron-based layered compound CeFePO. At temperatures from 9.4 to 293 K, no magnetic splitting was observed in the M\"ossbauer spectra of CeFePO indicating a paramagnetic phase of the Fe magnetic sublattice. All the spectra were fitted with a small quadrupole splitting, and the Debye temperature of CeFePO was found to be \sim448 K. The isomer shift at room temperature, 0.32 mm/s, was almost equal to those of LnFeAsO (Ln = La, Ce, Sm). Comparing s-electron density using the isomer shifts and unit cell volumes, it was found that the Fe of CeFePO has a similar valence state to other layered iron-based quaternary oxypnictides except LaFePO.
M?ssbauer Spectroscopy and X-ray Diffraction Study of 57Fe-Labeled Tetrachloroferrate(III)-Based Magnetic Ionic Liquids  [PDF]
Rolfe H. Herber,Israel Nowik,Mirco E. Kostner,Volker Kahlenberg,Christoph Kreutz,Gerhard Laus,Herwig Schottenberger
International Journal of Molecular Sciences , 2011, DOI: 10.3390/ijms12106397
Abstract: Four 57Fe-labeled tetrachloroferrates(III) of organic cations (1-butyl-3-methyl-imidazolium, 1-allyl-3-methylimidazolium, 1-methyl-1-propylpyrrolidinium, tetraphenyl-phosphonium) were examined by temperature-dependent M?ssbauer spectroscopy. The hyperfine and dynamic parameters of the iron(III) site were determined. Single crystal X-ray diffraction data of [Ph 4P][FeCl 4] were collected at four temperatures (295, 223, 173, and 123 K), and the dynamics of the iron atom inferred from the M?ssbauer data and the single crystal U i,j parameters have been compared.
M?ssbauer Spectroscopy Studies on Magnetic Properties for 57Fe-substituted Ni-Mn-Sn Metamagnetic Shape Memory Alloys  [PDF]
Rie Y. Umetsu,Kenji Sano,Kouji Fukushima,Takeshi Kanomata,Yusuke Taniguchi,Yasushi Amako,Ryosuke Kainuma
Metals , 2013, DOI: 10.3390/met3020225
Abstract: In order to investigate the Fe substituted effects on the magnetic properties of the Ni-Mn-Sn metamagnetic shape memory alloys, magnetization and the M?ssbauer spectroscopy measurements were carried out with using 57Fe-doped specimens of Ni 2Mn 1.48?x 57Fe xSn 0.52 ( x = 0.02, 0.04 and 0.08). Singlet-type M?ssbauer spectra were clearly observed for x = 0.02 and 0.04 just below the martensitic transformation temperature, T M, and above the Curie temperature, T C, in the austenite phase. It was clear that the magnetic state in the martensite phase just below T M was paramagnetic for x = 0.02 and 0.04. In further doped 57Fe to Ni 2Mn 1.48Sn 0.52, T C in the austenite phase slightly increased. However, the value of T M significantly decreased. As a result, martensite phase with small spontaneous magnetization directly transformed to the ferromagnetic austenite phase during heating for x = 0.08. These results obtained from the M?ssbauer spectra were consistent with the results of the magnetic measurements in this study and the phase diagram reported by Fukushima et al. for normal Fe-doped Ni 2Mn 1.48?xFe xSn 0.52 alloys. The breakdown of the general rule, in which the ferromagnetic shape memory alloys with larger value of the valence electrons per atom, e/ a, showed higher T M, was also appeared in Ni 2Mn 1.48?xFe xSn 0.52 alloys, being similar to Ni 2Mn 1?xFe xGa alloys.
Interplay between spin density wave and superconductivity in '122' iron pnictides: 57Fe M?ssbauer study  [PDF]
A. Blachowski,K. Ruebenbauer,J. Zukrowski,Z. Bukowski,M. Matusiak,J. Karpinski
Physics , 2011,
Abstract: Iron-based superconductors Ba0.7Rb0.3Fe2As2 and CaFe1.92Co0.08As2 of the '122' family have been investigated by means of the 14.41-keV Moessbauer transition in 57Fe versus temperature ranging from the room temperature till 4.2 K. A comparison is made with the previously investigated parent compounds BaFe2As2 and CaFe2As2. It has been found that Moessbauer spectra of these superconductors are composed of the magnetically split component due to development of spin density wave (SDW) and non-magnetic component surviving even at lowest temperatures. The latter component is responsible for superconductivity. Hence, the superconductivity occurs in the part of the sample despite the sample is single phase. This phenomenon is caused by the slight variation of the dopant concentration across the sample (crystal).
Caracteriza??o de argilas encontradas em solos de Terras Indígenas do RS com o auxílio da espectroscopia M?ssbauer de 57Fe
Pérez, C. A. S.;Gobbi, D.;Marcos, J. L. N.;Paduani, C.;Ardisson, J. D.;
Ceramica , 2004, DOI: 10.1590/S0366-69132004000200007
Abstract: clay samples collected from soils of indian territories of the middle plateau in rio grande do sul were analyzed with the aim to obtain characterization data and technical parameters for their potential use as raw material for ceramic products. the mineralogical study in samples by using the x-ray diffraction technique demonstrated that the predominant clay mineral is kaolinite. others minerals as quartz and rutile also are present in small amounts. chemical analysis shows low percentages for oxides of mg, mn, k, na, ca, cu and zn (overall percentages smaller than 0.97%). the samples also were analyzed with the 57fe m?ssbauer spectroscopy. the m?ssbauer spectra at room temperature confirm the presence of the mineral kaolinite. at 77 k they reveal the existence of the minerals goethite and hematite as ultrafine magnetic particles in a superparamagnetic state. the physical tests performed in the samples show that these soils are very fine material and present appropriate granulometric characteristics and plasticity, which can be taken in advantage for the production of materials for construction or production of ornamental artifacts.
Magnetic Dynamics of a Multiferroic with an Antiferromagnetic Layer  [PDF]
Svitlana V. Kondovych,Helen V. Gomonay,Vadim M. Loktev
Physics , 2013,
Abstract: Shape effects in magnetic particles are widely studied, because of the ability of the shape and the size to control the parameters of a sample during its production. Experiments with nano-sized samples show that the shape can affect also the properties of antiferromagnetic (AFM) materials. However, the theoretical interpretation of these effects is under discussion. We propose a model to study the shape-induced effects in AFM particles at the AFM resonance frequency. The Lagrange function method is used to calculate the spectrum of resonance oscillations of the AFM vector in a synthetic multiferroic (piezoelectric + antiferromagnet). The influence of the specimen shape on the AFM resonance frequency in the presence of an external magnetic field is studied. Conditions for a resonance under the action of an external force or for a parametric resonance to arise in the magnetic subsystem are considered.


物理学报 , 1992,
Abstract: 利用真空双源蒸镀法成功地制备了Fe/Pd金属超晶格,并对其结构和磁性进行研究。发现其比饱和磁化强度在固定Pd层30?不变时,随Fe层厚度减小而单调上升,这是界面处Fe对Pd的极化效应造成的,且得出0K下极化效应的等效Fe层厚度约为10?;低温下σ-T关系满足Bloch的T3/2定律,自旋波劲度系数随Fe层厚度减小而单调增大;居里温度则单调下降。57Fe内转换电子M?ssbauer谱(CEMS)的测量进一步证实极化效应的存在,而界面处Fe原子不存在磁性增强,也不存在“死层”效应。
Change of the charge modulation during superconducting transition in SmFeAsO(0.91)F(0.09) seen by 57Fe M?ssbauer spectroscopy  [PDF]
A. K. Jasek,K. Komedera,A. Blachowski,K. Ruebenbauer,H. Lochmajer,N. D. Zhigadlo,K. Rogacki
Physics , 2015, DOI: 10.1016/j.jallcom.2015.10.151
Abstract: Iron-based superconductor SmFeAsO(0.91)F(0.09) has been investigated by the 57Fe Moessbauer spectroscopy versus temperature with the special attention paid to the region of the superconducting transition at about 47 K. Modulation of the electron charge density was found. It leads to the development of the charge density wave (CDW) and electric field gradient wave (EFGW). The modulation of CDW is enhanced in the temperature region of the superconducting gap opening, while the amplitude of EFGW is partly suppressed within this temperature region. This effect is exactly opposite to the similar effect in Ba(0.6)K(0.4)Fe2As2 superconductor. Hence, it seems that d electrons contribute significantly to the Cooper pair formation in both compounds as EFGW is perturbed within the temperature region of the superconducting gap formation.
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