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Descripción
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| The static and dynamic magnetic macroscopic properties of bulk and nanocrystalline TbAl1:5Fe0:5 alloys have been investigated. In bulk state, this alloy is understood as a reentrant ferromagnet. This is characterized by a ferromagnetic Curie transition at 114 K, as deduced from magnetization including Arrott plots, higher than that of TbAl2. The reentrance is found at lower temperatures, below 54 K, with a cluster glass behavior setting in, deduced from the magnetization irreversibility. This is accompanied by an abrupt increase of the coercivity from 0.08 kOe to 15 kOe at 5 K, respect to the TbAl2 alloy. Room temperature M¿ossbauer spectroscopy confirms the paramagnetic state of such a bulk alloy. The spin dynamics within the disordered magnetic state is described by the AC-susceptibility which shows a Vogel-Fulcher law for the slowing down process. This is caused by a random anisotropy affecting the existing clusters. The production of milled TbAl1:5Fe0:5 alloys enhances the presence of magnetic disorder and results in the particle downsizing toward the nanocrystalline state (close to 10 nm). In this case, two frequency-dependent contributions exist, with different activation energies, one of them can not be described by ideal spin glass nor blocking/unblocking (nanoparticle) processes. In addition, the coercivity reduces to 1 kOe with the decrease of the size as a consequence of the existence of single domain particles. The results are explained by the intricate interplay between exchange interactions and magnetocrystalline anisotropy with disorder and size effects. | |
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Internacional
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Si |
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JCR del ISI
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Si |
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Título de la revista
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Journal of Magnetism And Magnetic Materials |
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ISSN
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0304-8853 |
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Factor de impacto JCR
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1,826 |
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Información de impacto
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Volumen
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326 |
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DOI
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10.1016/j.jmmm.2012.08.050 |
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Número de revista
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326 |
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58 |
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65 |
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