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Title

Dynamics of AC susceptibility and coercivity behavior in nanocrystalline TbAl1.5 Fe0.5 alloys

AuthorsRojas, D. P.; Fernández Barquín, L.; González Legarreta, L.; Chaboy, Jesús; Piquer, Cristina; Rodríguez Fernández, J.; Pedro, Imanol de
Issue Date2013
PublisherElsevier
CitationJournal of Magnetism and Magnetic Materials 326: 58-65 (2013)
AbstractThe 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 66 K, with a cluster glass behavior setting in, deduced from the magnetization irreversibility. This is accompanied by an abrupt increase in the coercivity from 0.08 kOe to 15 kOe at 5 K, with respect to the TbAl2 alloy. Room temperature Mössbauer 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 cannot be described by ideal spin glass nor blocking/unblocking (nanoparticle) processes. In addition, the coercivity reduces to 1 kOe with the decrease in 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. © 2012 Elsevier B.V.
Publisher version (URL)http://dx.doi.org/10.1016/j.jmmm.2012.08.050
URIhttp://hdl.handle.net/10261/73476
DOI10.1016/j.jmmm.2012.08.050
Identifiersdoi: 10.1016/j.jmmm.2012.08.050
issn: 0304-8853
Appears in Collections:(ICMA) Artículos
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