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

By A. Martinez, Jorge Spottorno Giner, A. Figueroa, F. Bartolome, L. M. Garcia, C. Prestipino, Antonio Hernando Grande and Patricia Crespo del Arco

Abstract

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

Topics: Física de materiales, Física del estado sólido
Publisher: 'American Physical Society (APS)'
Year: 2010
DOI identifier: 10.1103/PhysRevB.82.012406
OAI identifier: oai:www.ucm.es:41744
Provided by: EPrints Complutense

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