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Fang YN, Hahn H, Kobe S, Witte R, Singh SP, Feng T, Ghafari M. Modifying the transition temperature, 120 K ≤ T c ≤ 1150 K, of amorphous Fe 90-xCo xSc 10 with simultaneous alteration of fluctuation of exchange integral up to zero. Sci Rep 2019; 9:412. [PMID: 30675006 PMCID: PMC6344561 DOI: 10.1038/s41598-018-36891-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/28/2018] [Indexed: 11/13/2022] Open
Abstract
Amorphous (a-) Fe90−xCoxSc10 alloys have been produced by rapid quenching from the melt. The Curie temperature, TC, was determined using both mean field theory and Landau’s theory of second-order phase transitions in zero and non-zero external fields. The dependence of TC on the atomic spacing can be explained by the empirical Bethe-Slater curve. The value of TC of a- Fe5Co85Sc10, determined by the above theoretical approaches is 1150 K, which is the highest TC ever measured for amorphous alloys. The flattening of the measured normalized magnetization, M(T)/M(0), as a function of the reduced temperature, T/TC, is explained within the framework of the Handrich- Kobe model. According to this model the fluctuation of the exchange integral is the main reason for the flattening of M(T)/M(0). In the case of a-Fe90Sc10 without Co, however, the fluctuation of the exchange integral is dominant only at zero external field, Bex = 0. At Bex = 9 T, however, the fluctuation of the exchange integral has no conspicuous effect on the reduction of the magnetization. It is shown that at Bex = 9 T the frozen magnetic clusters control the behaviour of the reduced magnetization as function of T/TC. In contrast to other ferromagnetic alloys, where the flattening of M(T)/M(0) is characteristic for an amorphous structure, the a- Fe5Co85Sc10 does not exhibit any trace of the fluctuation of the exchange integral.
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Affiliation(s)
- Y N Fang
- Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - H Hahn
- Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing, 210094, China.,Institute for Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz- Platz 1, 76344, Eggenstein- Leopoldshafen, Germany
| | - S Kobe
- Technische Universität Dresden, Institut für Theoretische Physik, D-01062, Dresden, Germany
| | - R Witte
- Institute for Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz- Platz 1, 76344, Eggenstein- Leopoldshafen, Germany
| | - S P Singh
- Institute for Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz- Platz 1, 76344, Eggenstein- Leopoldshafen, Germany
| | - T Feng
- Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - M Ghafari
- Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing, 210094, China.
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