Abstract
Recently, a fluctuating mixed-valence state formally denoted as Fe2.5+ was observed in BaSmFe2O5+δ double-perovskite samples, having δ < 0.5 [J. Linden, P. Karen, A. Kjekshus, J. Miettinen, T. Pietari, M. Karppinen, Phys. Rev. B 60 (1999) 15251.]. Upon cooling such samples to the Verwey-type transition temperature (TV ≈ 200 K), a mixing-separation transition of the valence state occurs. In order to study in detail the formation of the mixed-valence state BaSm(Cu0.5+xFe0.5-x)2O5+δ, samples with a certain amount of Fe (0-10% and 40-50%) replaced by Cu have been characterized by 57Fe Mossbauer spectroscopy and magnetization measurements. All samples were found to be magnetically ordered at room temperature. The amount of Fe entering the Fe2.5+ state decreased rapidly as the Cu doping level was increased, as judged by the Mossbauer spectra. Increasing the Cu concentration also led to an increase of TV.
| Original language | English |
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| Pages (from-to) | 126-131 |
| Number of pages | 6 |
| Journal | Physica C: Superconductivity and its Applications |
| Volume | 338 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 1 Aug 2000 |
| MoE publication type | A4 Conference publication |
| Event | International Discussion Meeting on Chemistry Approaches to High-Tc Superconductive Materials & 5th International Workshop on Chemical Designing and Processing of High-Tc Superconductors (Chem-HTSC-V) - Yokohama, Japan Duration: 15 Oct 1999 → 16 Oct 1999 |
Funding
One of the authors (J.L.) acknowledges kind support from the Japan Society for the Promotion of Science. The present work has been supported by a Grant-in-Aid for Scientific Research (contract No. 11305002) from The Ministry of Education, Science and Culture of Japan, and also by an International Collaborative Research Project Grant-1999 of the Materials and Structures Laboratory, Tokyo Institute of Technology.