Effect of rapid quenching on the magnetism and magnetocaloric effect of equiatomic rare earth intermetallic compounds RNi (R = Gd, Tb and Ho)
| Autor: | Satish K. Malik, R. Nirmala, R. Rajivgandhi, S. Quezado, J. Arout Chelvane |
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| Rok vydání: | 2017 |
| Předmět: |
010302 applied physics
Quenching Materials science Condensed matter physics Magnetism Intermetallic 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics Microstructure 01 natural sciences Electronic Optical and Magnetic Materials Crystallography Magnetization 0103 physical sciences Magnetic refrigeration Orthorhombic crystal system 0210 nano-technology Monoclinic crystal system |
| Zdroj: | Journal of Magnetism and Magnetic Materials. 433:169-177 |
| ISSN: | 0304-8853 |
| Popis: | Magnetocaloric effect (MCE) in RNi (where R = Gd, Tb and Ho) compounds has been studied in their arc-melted and melt-spun forms. The compound GdNi has the orthorhombic CrB-type structure (Space group Cmcm, No. 63) and the compound HoNi has the orthorhombic FeB-type structure (Space group Pnma, No. 62) at room temperature regardless of their synthesis condition. However, arc-melted TbNi orders in a monoclinic structure (Space group P21/m, No. 11) and when it is rapidly quenched to a melt-spun form, it crystallizes in an orthorhombic structure (Space group Pnma, No. 62). The arc-melted GdNi, TbNi and HoNi compounds order ferromagnetically at ∼69 K, ∼67 K and ∼36 K (TC) respectively. While the melt-spun GdNi shows about 6 K increase in TC, the ordering temperature of TbNi remains nearly the same in both arc-melted and melt-spun forms. In contrast, a reduction in TC by about 8 K is observed in melt-spun HoNi, when compared to its arc-melted counterpart. Isothermal magnetic entropy change, ∆Sm, calculated from the field dependent magnetization data indicates an enhanced relative cooling power (RCP) for melt-spun GdNi for field changes of 20 kOe and 50 kOe. A lowered RCP value is observed in melt-spun TbNi and HoNi. These changes could have resulted from the competing shape anisotropy and the granular microstructure induced by the melt-spinning process. Tailoring the MCE of rare earth intermetallic compounds by suitably controlled synthesis techniques is certainly one of the directions to go forward in the search of giant magnetocaloric materials. |
| Databáze: | OpenAIRE |
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