Martinez, A.Spottorno Giner, JorgeFigueroa, A.Bartolome, F.Garcia, L. M.Prestipino, C.Hernando Grande, AntonioCrespo del Arco, Patricia2023-06-202023-06-202010-07-141098-012110.1103/PhysRevB.82.012406https://hdl.handle.net/20.500.14352/42610©2010 The American Physical Society. This work was supported by Spanish MICINN under Projects No. MAT2009-14741-C02-01 and No. MAT2008- 01077, and Consolider-Ingenio in Molecular Nanoscience under Project No. CSD2007- 00010; and DGA by means of IMANA and CAMRADS. A.I.F acknowledges a CSIC-JAE Predoc grant.Amorphous metastable alloy of nominal composition [Fe_(0.5)Cu_(0.5)]_(87)Zr_(13) has been synthesized by high-energy ball milling. The alloy exhibit a ferromagnetic behavior with a Curie Temperature of T_(C)=255 K, as determined from low-field measurements whereas no transition to a paramagnetic state is observed under high- enough applied magnetic fields. The evolution of hysteresis loops with temperature as well as thermoremanence measurements indicate an anomalous magnetic behavior characterized by a spontaneous increase in the magnetization values as well as by a magnetic hardening when the temperature is increased above T_(C). These effects are strongly correlated with a dilation of the Fe-Fe nearest-neighbor distances, as determined from extended x-ray absorption fine structure (EXAFS) studies. EXAFS results indicate an almost negligible thermal expansion at temperatures below T_(C) while normal thermal expansion takes place at higher temperatures. Such expansion seems to promote a reinforcement of the ferromagnetic interactions among Fe-Fe atoms that would account for the observed spontaneous increase in the magnetization as well as for the evolution of the coercive field.engjournal articlehttp://dx.doi.org/10.1103/PhysRevB.82.012406http://journals.aps.orgopen access538.9SemiconductorsFerromagnetismNanoparticlesFísica de materialesFísica del estado sólido2211 Física del Estado Sólido