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Mg, Smith; Rd, Taylor; Óesterreicher, H.

doi:10.1103/physrevb.42.4202

Cited by 81 publications

(3 citation statements)

References 15 publications

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“…The behavior of the D-2 component allows us to suppose that the transition from the y=0.5 to the y=0.0 state arises sharply at 400 ° C and the number of the oxygenordering chain sites increases [6]. However, not all of the Cu atoms can achieve the V4 coordination and it is likely that oxygen vacancies occur at the boundaries separating ordered regions, with V 3 and V5 coordinated copper located at these boundaries.…”

Section: M6ssbauer Measurementsmentioning

confidence: 98%

57Fe M�ssbauer study of YBa4Cu2.95Fe0.05O8.5+y

et al. 1991

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Abstract. 57Fe Mtssbauer measurements were performed on the Fe-doped YBa4Cu3Os.5+y compound as a function of annealing temperature in vacuum. Mtssbauer spectra were analyzed using three different quadrupole split doublets. The resistance measurements showed that the compound is not superconducting. The possible identification of the Cu sites with their nearest neighbor oxygen sites in this compound is suggested. Comparison of the results with data of the presence of the superconductor YBa2Cu30 7 allows us to suppose that the presence of the Cu-chain sites alone does not result in superconductivity.PACS: 74.70.Vy, 76.80.+yThe discovery of high-T~ superconductivity in the YBa2Cu307 (named 1-2-3) compound has stimulated considerable effort to identify the different compounds and phases in the YzO-BaO-CuO system [-1, 2]. Most of them have been identified and possible crystal structures presented. For one of them, YBa4Cu308.5+ r (named 1-4:3), the positions and occupation numbers of especially the oxygen ions were determined by neutron powder diffraction measurements [2]. In contrast to the 1-2-3 compound, in the 1-4-3 structure there are only Cu-chain sites along all three crystallographic axes.In this report the Mtssbauer study of the Fe-doped 1-4-3 compound is presented as a function of annealing temperature in vacuum. Comparing the obtained results with data for the 1-2-3 compound we attempted to establish the role of Cu-chain and Cu=plane sites in the high-To superconducting transition. It is shown that the presence of Cu-chain sites alone does not result in superconductivity.

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Section: M6ssbauer Measurementsmentioning

confidence: 98%

57Fe M�ssbauer study of YBa4Cu2.95Fe0.05O8.5+y

et al. 1991

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“…The invariance upon the substitution level could be due to the formation of Fe clusters whose structure would not be dependent upon Fe concentration. It is known that the thermal treatment affects the occupancy of sites Cu(1) and Cu(2) by Fe [2] and on the other hand the value of 0 is strongly dependent on the occupancy. The results support our assumption that the treatment denoted as Set II leads to a lower degradation of superconducting properties in the Fe-doped samples.…”

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confidence: 99%

“…It is known that there are two different Cu crystallographic sites in the structure Cu(1) chains and Cu(2) plane and it is conceivable that the site occupancies may vary as a function of concentration or a specific sample preparation method. A synthesis of YBa2(C1l_x F e x ) 3 0 y under relatively reducing conditions (inert atmosphere) and subsequent careful low-temperature annealing in O2 produce material with a lower ratio of Fe in the Cu(1) and Cu(2) site compared with a conventionally prepared material [2]. On the other hand, the accumulation of crystal strain during milling is changing the lattice parameter, sinterability, transport and magnetic properties [3,4].…”

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Magnetic Properties of Milled and Thermal Relaxed YBa₂(Cu_1-xFe_x)₃O_y

et al. 1997

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The influence of the mechanical milling and subsequent thermal relaxation on magnetic and superconducting behaviour of YBa2(Cu1_ y F e x ) 3 O y system has been studied. Two methods of heat treatment were used: Set I -slow cooling from 980°C in flowing O2 and Set H -reducing at 770°C in flowing Are followed by reoxidation in flowing O2 below 400°C. The transition to superconductivity, diamagnetic response, critical current density and the effective magnetic moment in the normal state have been estimated. Our measurements indicate that the reducing atmosphere preparation is less detrimental on superconducting properties. The results are discussed in terms of occupancy Cu sites by Fe and redistribution of oxygen atoms.PACS numbers: 74.10.+v, 74.70.-b, 74.90.+n A substitution of Fe for Cu in YBa 2(Cu1_xFex)3Oy has attracted a large interest because of the iron influence on superconductivity, microstructure and magnetic properties. The microstructure of doped samples is twinned for x < 0.015, twinned and tweed for 0.015 < x < 0.03, and tweed for x > 0.03, where tweed is a fine scale orthogonal microstructure [1]. It is known that there are two different Cu crystallographic sites in the structure Cu(1) chains and Cu(2) plane and it is conceivable that the site occupancies may vary as a function of concentration or a specific sample preparation method. A synthesis of YBa2(C1l_x F e x ) 3 0 y under relatively reducing conditions (inert atmosphere) and subsequent careful low-temperature annealing in O2 produce material with a lower ratio of Fe in the Cu(1) and Cu(2) site compared with a conventionally prepared material [2]. On the other hand, the accumulation of crystal strain during milling is changing the lattice parameter, sinterability, transport and magnetic properties [3,4].In this paper we are reporting superconducting and magnetic properties of milled and thermal relaxed YBa2(Cui1_xFex)3Oy (x = 0.0 and 0.04) powder after different thermal treatments in superconducting and normal state.Powders of nominal composition YBa2(Cu1_xFex)3Oy were prepared in crushed, milled and milled & relaxed states [5]. The sintered powders were treated by two methods. The conventional method (denoted as Set I) involved annealing (355)

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