Positron annihilation studies in single and polycrystals of Zn1−xCuxCr2Se4spinel series

Groń, T.; Wolff, Joachim R.; Hehenkamp, Th.; Bärner, K.; Okońska‐Kozłowska, I.; Jendrzejewska, Izabela; Malicka, E.

doi:10.1080/10420159608211538

Cited by 8 publications

(20 citation statements)

References 19 publications

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“…Crystallographical specificity of spinel structure reflects in the shortest lifetime component, while the middle component corresponds to vacancy-like defects near grain boundaries.1 Introduction Sintered spinel-type ceramics have been widely used as one of the most perspective materials for multifunctional device application [1][2][3][4][5]. Because of significant complications in the structure of these ceramics revealed at the levels of individual grains, intergrain boundaries and pores [6], the further progress in this field is dependent to a great extent on the development of new characterization techniques, which can be used in addition to traditional ones.…”

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confidence: 99%

Defect characterization methodology in sintered functional spinels with PALS technique

Balitska

Filipecki

Ingram

et al. 2007

Phys. Status Solidi (c)

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It is shown that extended free-volume defects in sintered functional spinels can be well characterized with positron annihilation lifetime spectroscopy, provided obtained data are treated in terms of unified multichannel positron annihilation model involving both positron trapping and ortho-positronium decay modes. Crystallographical specificity of spinel structure reflects in the shortest lifetime component, while the middle component corresponds to vacancy-like defects near grain boundaries.1 Introduction Sintered spinel-type ceramics have been widely used as one of the most perspective materials for multifunctional device application [1][2][3][4][5]. Because of significant complications in the structure of these ceramics revealed at the levels of individual grains, intergrain boundaries and pores [6], the further progress in this field is dependent to a great extent on the development of new characterization techniques, which can be used in addition to traditional ones. This concerns, in part, the positron annihilation lifetime spectroscopy (PALS), the method only recently applied to fine-grained powders and ceramics [7].In general, the PALS being it sensitive to low electron density reflects a so-called void-species distribution within structural network of solids [7]. But meaningful interpretation of PALS data is well reliable only for some types of crystals. It was shown that in the case of ceramics these data were determined mainly by crystallographical features of individual grains, while structural disturbances due to intergranular contacts within ceramics were a subject for additional complications [2][3][4]7]. That is why the measured positron lifetime spectra for sintered ceramics can be adequately explained within a unified multi-channel positron annihilation model involving discrete positron trapping and ortho-positronium (oPs) decay modes, the best fitting being achieved using at least 3 independent components in the resolved lifetime spectra (two for positron trapping and one for o-Ps decaying) [2][3][4]8]. In terms of this model, the second positron trapping component with τ 2 = 0.3-0.5 ns lifetimes is attributed to free-volume defects such as neutral or negatively-charged vacancies especially near grain boundaries. The shortest component named the reduced bulk positron lifetime τ 1 is mainly due to annihilation in defect-free bulk with small mixing from other positron trapping channels. The largest component at the level of a few nanoseconds is responsible for a so-called o-Ps "pick-off" annihilation [7].

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confidence: 99%

Defect characterization methodology in sintered functional spinels with PALS technique

Balitska

Filipecki

Ingram

et al. 2007

Phys. Status Solidi (c)

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“…12-14 show the specific heat for Zn x Dy y Cr z Se 4 (y¼0.05, 0.13, 0.19) with sharp peak at T N for H ¼0, which is strongly shifted to much lower temperatures in the applied magnetic fields, similar to the sharp peak observed for the ZnCr 2 Se 4 matrix [9]. The specific heat plotted in the representation C/T vs. T (Figs.…”

Section: Spinelmentioning

confidence: 56%

“…No split of the The magnetization isotherms presented in Figs. 9-11 show the metamagnetic transition at the first critical field H c1 , and the breakdown of the helical spin arrangement at the second critical field H c2 , as it was observed in ZnCr 2 Se 4 [9,15] matrix, ZnCr 2-x Al x Se 4 polycrystals [16] and single crystals [17]. H c1 does not depend on the temperature for y¼0.05, but strongly decreases with increasing temperature for the samples richer in dysprosium.…”

Section: Magnetic Propertiesmentioning

confidence: 65%

“…Next, the FM exchange interaction with parallel spins in the (001) planes strongly weakens with increasing temperature. It finally leads to the disappear of the AFM and FM competitions and spin glass does not appear, as it is observed in the ZnCr 2 Se 4 matrix [9].…”

Section: Magnetic Propertiesmentioning

confidence: 78%

“…In a number of papers it has been presented that replacement of di-or trivalent cations by other metals results in essential changes in the physical properties, where effect of polaron conductivity, lattice frustration or spin-glass-behavior could be observed [7][8][9][10][11]. On the other hand, the spinel compounds based the ZnCr 2 Se 4 doped with rare-earth-elements are almost unknown.…”

Section: Introductionmentioning

confidence: 97%

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