Crystal structure and magnetism of layered Ln2Ca2MnNiO8 (Ln=Pr,Nd, Sm,and Gd) compounds |
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| Affiliation: | 1. Department of Chemistry and BK-21 School of Molecular Science, Sungkyunkwan University, Suwon 440-746 South Korea;2. Department of Chemistry, Konkuk University, Seoul 143-701 South Korea;3. Korea Atomic Energy Research Institute, Daejon 350-600 South Korea;1. Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Tsushima, Kita-ku, Okayama 700-8530, Japan;2. Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Tsushima, Kita-ku, Okayama 700-8530, Japan;1. Center for Condensed Matter & Beijing Key Laboratory of Metamaterials and Devices, Department of Physics, Capital Normal University, Beijing 100048, China;2. State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;1. College of Materials Science and Engineering, Shandong Jianzhu University, Jinan 250101, China;2. Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan, 250061, China;1. Physics Department, College of Science & Arts, Najran University, P. O. 1988, Najran, Saudi Arabia;2. Reactor Physics Department, NRC, Atomic Energy Authority, Abou Zabaal P.O. 13759, Cairo, Egypt;3. Physics Department, Faculty of Science, Sohag University, Sohag 82524, Egypt;4. Physics Department, Aljamoum University College, Um-Elqura University, Makka, Saudi Arabia;5. Physics Department, Faculty of Science, Soltan Qaboos University, P.O. Box 36, PC 123, Muscatt, Oman;1. Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice, Poland;2. Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, Al. Piastów 42, 71-065 Szczecin, Poland |
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| Abstract: | We report the syntheses, crystal structure, and magnetic properties of a series of distorted K2NiF4-type oxides Ln2Ca2MnNiO8 (Ln=Pr, Nd, Sm, and Gd) in which Ln/Ca and Mn/Ni atoms randomly occupy the K and Ni sites respectively. The Ln=La compound does not form. These compounds show systematic distortions from the ideal tetragonal K2NiF4 structure (space group I4/mmm) to an orthorhombic structure (space group Pccn) with buckled MO2 (M=Mn/Ni) layers. The degree of distortion is increased as the size of Ln decreases. Based on the magnetic data and X-ray absorption near edge spectra, we assigned MnIV and NiII. The Curie–Weiss plots of the high temperature magnetic data suggest strong ferromagnetic interactions probably due to MnIV–O–NiII linkages, implying local ordering of Mn/Ni ions to form ferromangnetic clusters in the MO2 layers. At low temperatures below 110–130 K, these compounds show antiferromagnetic behaviors because of MnIV–O–MnIV and/or NiII–O–NiII contacts between the ferromagnetic clusters. The Ln=Pr and Nd compounds show additional antiferromagnetic signals that we attribute to the interlayer interactions between the clusters mediated by the Pr3+ and Nd3+ ions in the interlayer spaces. The present compounds show many parallels with the previously reported Ln2Sr2MnNiO8 compounds. |
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