Journal de Physique et le Radium最新文献_第6页

Diffusion des neutrons froids par les phonons dans le nickel 冷中子通过声子在镍中的扩散

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505065301

S. Hautecler, W. V. Dingenen

引用次数: 3

Structure magntique des composs RIr2 Terres rares Iridium 稀土铱复合材料的磁性结构

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505061401

G. Felcher, W. Koehler

引用次数: 0

L'interaction magntique dans les structures de K2NiF4 K2NiF4结构中的磁相互作用

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505057801

E. Legrand, M. Verschueren

引用次数: 10

Redetermination of the cation distribution of spinel (MgAl2O4) by means of neutron diffraction 用中子衍射法重新测定尖晶石(MgAl2O4)的阳离子分布

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505044700

E. Stoll, P. Fischer, W. Hälg, G. Maier

{"title":"Redetermination of the cation distribution of spinel (MgAl2O4) by means of neutron diffraction","authors":"E. Stoll, P. Fischer, W. Hälg, G. Maier","doi":"10.1051/JPHYS:01964002505044700","DOIUrl":"https://doi.org/10.1051/JPHYS:01964002505044700","url":null,"abstract":"2014 The cation distribution of synthetic spinel powder of grain size ~ 50 03BC was redetermined by means of neutron diffraction experiments. The oxygen parameter found by Bacon (1952) has been confirmed, but, in contradiction to Bacon, the degree of inversion amounts to about 10 to 15 %, and depends upon the thermal history of the sample. LE JOURNAL DE PHYSIQUE TOME ‘~5, MAI 196~, Magnesium aluminium oxyde crystallizes in the space group Fd3n?. The unit cell can be described by a nearly close packed cubic oxygen arrangement with built-in cations, which are either tetrahedrally or almost octahedrally surrounded by the oxygen atoms. The lattice parameter of the unit cell amounts to 8.0832 A, and there are eight molecules per cell. The spinel structure is characterized by the fact that, relative to the center of symmetry, the cations are located at fixed positions, while the oxygen positions depend upon a parameter u. The spinel structure is called \" normal \" if the Mg atoms occupy the tetrahedral A-sites, only. However, on the space average, any fraction of Mg can be replaced by Al atoms. This fraction of replacement is called \" degree of inversion \" and denoted by i. The knowledge of the degree of inversion, and thus of the cation distribution, is of special interest in connection with possible changes of the structure due to the thermal history of the substance. Thus far, two basically different methods have been employed for the problem in question. One is to use nuclear resonance techniques, as was done by Brun and coworkers [1]. They found that synthetically produced Mg-Al spinels are considerably inverse, while naturally grown Mg-Al spinels exhibit approximately the normal spinel structure, when not annealed beyond about 800 °C. However, once annealed at temperatures higher than 800 OC, natural spinel will be inverse to a large degree. A second, and more reliable method to determine the degree of inversion, and thus the cation distribution, is provided by neutron diffraction. From the equation of the structure factor where and = iiinctions of u, i .--degree of inversion and = inn-lear scattering amplitude, it follows that L can be obtained with accuracy, since the b-values of the two cation constituents differ considerably. Bacon [2] was the first to use the above relationship in order to determine the degree of inversion in synthetic spinel powder samples. He found, in contradiction to Brun and coworkers, a nearly vanishing i-value, i. e. a normal spinel structure with at most a slight tendency towards inversion. Because of this discrepancy, it appeared desirable to repeat the neutron diffraction experiments, and to investigate the effect of annealing the sample on its structure. Since Bacon could, in 1952, perform his diffraction work with low resolution only, the aim in our experiments was to improve the resolution. The investigations were performed with the 20 MW reactor \" Diorit \" of the Swiss Federal Institute for Reactor Research. Syn","PeriodicalId":54899,"journal":{"name":"Journal de Physique et le Radium","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1964-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88704660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 44

Neutron diffraction study of nickel zirconium hydride 氢化锆镍的中子衍射研究

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505045100

S. W. Peterson, V. Sadana, W. L. Korst

引用次数: 57

Structure magntique de -FeNao2 et affinement des positions atomiques -FeNao2的磁性结构和原子位置的细化

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505054500

E. F. Bertaut, A. Delapalme, G. Bassi

{"title":"Structure magntique de -FeNao2 et affinement des positions atomiques","authors":"E. F. Bertaut, A. Delapalme, G. Bassi","doi":"10.1051/JPHYS:01964002505054500","DOIUrl":"https://doi.org/10.1051/JPHYS:01964002505054500","url":null,"abstract":"2014 In orthorhombic 03B2-FeNaO2, (a0 = 5.672 ; b0 = 7.136 ; c0 = 5.377 Å ; group Pna) each Fe atom has four near Fe neighbors with antiparallel spins. The axis of antiferromagnetism is Oz. A weak ferromagnetic component is associated along Oy. Structure refinement confirms the tetrahedral coordination of Na, proposed by Bertaut and Blum. LE JOURNAL DE PHYSIQUE TOME :2 5, MAI 1 196~, Introduetion. Le ferrite de sodium FeNa02 existe sous tpois formes. La structure [1] de cx:-FeNa02 est rhomboédrique (a = 5,59 A ; oc = 31°20’) appartient au groupe centrosymétrique .R 3 m (-D’3d) et possède des octaèdres de coordination autour des cations Fe3 v et N a + . La structure [2] de composé découvert par Dodero et Desportes [3] est orthorhombique (a = 5,672 A ; b = 7,136 A ; c = 5,377 A ; Dx = 3,36), pseudo-quadratique (a c), appartient au groupe non centré pna (C’,) et possède des tétraèdres de coordination autour des deux sortes de cations. Enfin une troisième variété, quadratique, y-FeNa02 très proche de g-FeNa02 a été signalée assez récemment [4]. La forme oc, stable à l’ambiante, se transforme en forme B vers 600 °C. La transition p y se situe vers 1 103 °C. La transformation est remarquable par sa considérable expansion de volume moléculaire lequel augmente de V = 42,2 Â3 à V = 54,4 A3, soit de 29 %. L’explication de l’expansion réside en ce que dans la forme oc les octaèdres de coordination ont des arêtes communes tandis que dans la forme ~ les tétraèdres de coordination n’ont que des sommets communs. Dans cette étude nous déterminons d’abord la configuration magnétique des spins dans Nous précisons ensuite les paramètres de position provisoires donnés dans la référence [2]. Un tel raffinement nous a paru d’ailleurs d’autant plus nécessaire qu’une coordination tétraédrique autour d’un cation Na+ est exceptionnelle et demande","PeriodicalId":54899,"journal":{"name":"Journal de Physique et le Radium","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1964-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74586871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 21

Problems and procedures in collection of three-dimensional neutron diffraction data for crystal structure determination 晶体结构测定用三维中子衍射数据收集中的问题和程序

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505049700

G. Brown, H. A. Levy

引用次数: 4

Structures of UO2, UO2+x andU4O9 by neutron diffraction UO2, UO2+x和u4o9的中子衍射结构

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505043100

B. Willis

{"title":"Structures of UO2, UO2+x andU4O9 by neutron diffraction","authors":"B. Willis","doi":"10.1051/JPHYS:01964002505043100","DOIUrl":"https://doi.org/10.1051/JPHYS:01964002505043100","url":null,"abstract":"Single crystals have been examined by neutron diffraction in the range of temperatures 20 °C to 1 100 °C and of compositions UO2 to U4O9. The investigations divide into three groups, relating to UO2, UO2+x (where 0 (for O') and along (for O\") from the large interstices in the fluorite structure. The interstices themselves are not occupied. At the composition UO 2.25 the oxygen atoms are ordered to form the new phase U4O9. The \" main \" neutron reflexions of U4O9, corresponding to the fluorite-type peaks of UO2, are much stronger than the superlattice reflexions, which arise from the ordering of the interstitial oxygen atoms within the fluorite framework. The analysis of the intensities of the main reflexions shows that there are two kinds of interstitial sites, as in UO2+x : the 0' atoms are located 0.85 A along the directions from the centres of the large interstices, and the O\" atoms 1.05 A along . Vacancies occur in the fluorite-type oxygen sites (0) but not in the uranium sites, and the chemical formula UO2.25 is expressed more fully as U1.00 O1.77 O'0.29 O\"0.19. It is concluded that oxygen atoms cannot enter the fluorite structure individually but are incorporated in small groups containing O' and O\" atoms and O vacancies. A complete structure determination of U4O9 must await the analysis of the superlattice reflexions.","PeriodicalId":54899,"journal":{"name":"Journal de Physique et le Radium","volume":"181 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1964-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88443234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 166

Neutron diffraction studies of magnetic moments in dilute transition metal alloys 稀过渡金属合金磁矩的中子衍射研究

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505059600

M. Collins, G. Low

引用次数: 23

Magnetic structure of binary fluorides containing Mn2 含Mn2的二氟化物的磁性结构

Journal de Physique et le Radium Pub Date : 1964-05-01 DOI: 10.1051/JPHYS:01964002505056500

S. Pickart, H. Alperin, R. Nathans

{"title":"Magnetic structure of binary fluorides containing Mn2","authors":"S. Pickart, H. Alperin, R. Nathans","doi":"10.1051/JPHYS:01964002505056500","DOIUrl":"https://doi.org/10.1051/JPHYS:01964002505056500","url":null,"abstract":"2014 Spin orderings of the binary fluorides with chemical formula XMnF3 (X = Na, Rb, Cs, and NH4) were investigated by neutron diffraction. The antiferromagnetic lattices of the compounds with X = Na, Rb, and NH4 are found to be of the same basic type as found in KMnF3 (G-type). In CsMnF3, which is hexagonal, the Mn2+ layers are arranged in an antiparallel sequence along the c-axis, with the spin direction normal to the axis. LE JOURNAL DE PHYSIQUE TOME 25, MAI 196fit, Introduction. Binary fluorides of the type XMnF (X = Na, Rb, Cs, and NH4), which were investigated previously by means of x-ray [1, 2], electron spin resonance [3, 4] specific heat [5], and magnetization [6, 7] measurements, have been reported to be antiferromagnetic. The present study reports powder neutron diffraction measurements on these compounds undertaken to confirm the antiferromagnetism and to study details of the magnetic ordering. Some information was also obtained concerning the nuclear structures. Experimental. The measurements were taken on powdered samples, which were kindly furnished by M. Shafer. Temperatures intermediate between 4.2 oK and 77 oK were attained by heating the sample holder, which was insulated from the liquid helium bath by thin teflon sheets, or by pumping on liquid nitrogen. In this way the sample could be held at any desired temperature, which was measured by a carbon resistance thermometer in contact with the sample holder. For small temperature changes, the sample came into equilibrium after about one-half hour. Structure information. All of the compounds can be considered as based on perovskite. RbMnF3 and NH4MnF3 are cubic (tolerance ratios 1.00 and 0.97, respectively), while NaMnF3 and CSNInF have tolerance ratios outside the cubic range. The Na compound is orthorhombic [1] and has a pseudomonoclinic cell derived from a (1) Work performed under the auspices of the U. S. Atomic Energy Commission. slight distortion of the cubic cell ; the Cs compound is hexagonal [2], with the ABCABC stacking of the cubic phase altered to ABCACB, in analogy with the hexagonal form of BaTio3’ In the case of RbMnF3 we observe only cubic perovskite reflections, as expected. However, if the tabulated nuclear scattering amplitudes ~ bRb = bF = 0.55) are used, there is a small discrepancy between weak reflections which can be removed only by making bRb > bF. Indications are that bxb should be increased to about 0. 63. The hydrogen positions in NH4IVInF3 should be obtainable from the neutron data. Good agreement ~~ == 0 .044) was obtained by distributing the hydrogen statistically in the twelvefold position 12(1) of Pm3m, i.e., along the direction toward the neighboring F ions. The N-H distance is 1.14 ~., which is slightly larger than that found [8] in NH4Cl and ND4Cl. The nuclear scattering from the CsMnF3 was examined to see if any change in the fluorine parameters might be required. Using the x-ray parameters determined by Zalkin et al. [2], we obtained an R","PeriodicalId":54899,"journal":{"name":"Journal de Physique et le Radium","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1964-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88971490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 18