Direct measurements of the correlation between reentrant ferromagnetism and lattice expansion in FeCuZr alloys



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Martinez, A. and Spottorno Giner, Jorge and Figueroa, A. and Bartolome, F. and Garcia, L. M. and Prestipino, C. and Hernando Grande, Antonio and Crespo del Arco, Patricia (2010) Direct measurements of the correlation between reentrant ferromagnetism and lattice expansion in FeCuZr alloys. Physical review B, 82 (1). ISSN 1098-0121

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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.

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©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.

Uncontrolled Keywords:Semiconductors; Ferromagnetism; Nanoparticles
Subjects:Sciences > Physics > Materials
Sciences > Physics > Solid state physics
ID Code:41744
Deposited On:10 Mar 2017 15:48
Last Modified:14 Feb 2018 14:37

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