Atomic Charge States in Tl2Ba2Can?1CunO2n+4 as Determined by the61Cu(61Ni),67Cu(67Zn) and133Ba(133Cs) Emission M�ssbauer Spectroscopy

Abstract

Parameters of the electric field gradient tensors have been found for the Cu and Ba sites of the Tl 2 Ba 2 Ca nÀ1 Cu n O 2n4 lattices by the 61 Cu 61 Ni, 67 Cu 67 Zn and 133 Ba 133 Cs emission Mo È ssbauer spectroscopy. The same parameters have been calculated using the point charge approximation. An analysis of the obtained quantities has been carried out taking into consideration literature data on the 63 Cu nuclear quadrupole resonance. Agreement of the measured and calculated parameters could be reached assuming the holes resulting from lowering the valence of part of the Tl atoms to be placed mainly at oxygen sites of the Cu±O planes (especially, at oxygen sites of the Cu(2)±O planes for the Tl 2 Ba 2 Ca 2 Cu 3 O 10 compound).wetodom Cmissionnoj messuzrovskoj spektroskopii n izotoph 61 Cu 61 NiD 67 Cu 67 Zn i 133 Ba 133 Cs opredeleny prmetry tenzor grdient Clektriqeskogo pol¾ v uzlh medi i ri¾ rexetok Tl 2 Ba 2 Ca nÀ1 Cu n O 2n4 D tkwe proveden rsqet ukznnyh prmeE trov v priliwenii toqeqnyh zr¾dovF roveden nliz poluqennyh veliqin s privleE qeniem literturnyh dnnyh po ¾dernomu kvdrupol5nomu rezonnsu n izotope 63 Cu X soglsovnie Cksperimentl5nyh i rsqetnyh prmetrov dostigets¾D esli predpoloE wit5D qto dyrkiD po¾vl¾Ï §ies¾ v rezul5tte poniweni¾ vlentnosti qsti tomov tlE li¾D loklizuÏts¾ preimu §estvenno n uzlh kislorodD nhod¾ §ihs¾ v odnoj ploskosti s tommi medi @dl¾ soedineni¾ Tl 2 Ba 2 Ca 2 Cu 3 O 10 ± ± n uzlh kislorodD nhod¾ §iks¾ v odnoj ploskosti s tommi Cu2F

Spatial distribution of Bose condensate in high-temperature superconductors, determined by emission M$ouml$ssbauer spectroscopy

“…The quadrupole interaction constants C were found to be virtually temperatureindependent for all the ceramics. This is an expected result, because the electric field gradient the 67 Zn 2+ probe is produced by the lattice ions only [8][9][10][11], and variations of the lattice constants in the temperature range 4.2-80 K are negligibly small [13,14].…”

“…Typical spectra of the La 1.85 Sr 0.15 CuO 4 ceramics are shown in figure 1. The proposed interpretation of the 67 Cu( 67 Zn) spectra assumes that parent 67 Cu atoms occupy copper sites upon diffusion doping, which is confirmed by [8][9][10], and, therefore, the 67 Zn 2+ probe produced in 67 Cu decay occupies the copper site, too. For the La 1.85 Sr 0.15 CuO 4 : 67 Ga spectra, it was assumed that the diffusion doping causes parent 67 Ga atoms to occupy lanthanum sites, and, therefore, the 67 Zn 2+ probe formed in 67 Ga decay also occupies the lanthanum site.…”

“…Both of the above requirements are satisfied for 67 Cu( 67 Zn) emission Mössbauer spectroscopy with 67 Zn probe in copper metaloxide lattices. The δ/G value is estimated to be 50-200 for 67 Zn, and parent 67 Cu atoms occupy copper sites in synthesis, so that daughter 67 Zn atoms are situated at the same lattice sites [8][9][10]. In addition, another parent nucleus 67 Ga used in 67 Ga( 67 Zn) emission Mössbauer spectroscopy allows one to introduce the 67 Zn probe at rare-earth sites [11] of high-temperature superconductors containing rare-earth metals, thus making it possible to study the spatial nonuniformity of the electron density created in Bose condensation of Cooper pairs.…”