Magnetic properties of nanostructured powders, nanowires and thin films based on FeRh alloys

• Grant number: 09/02348-9
• Support Opportunities: Regular Research Grants
• Start date: May 01, 2009
• End date: April 30, 2011
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Daniel Reinaldo Cornejo
• Grantee: Daniel Reinaldo Cornejo
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

FeRh alloys, near to the equiatomic composition, present the uncommon characteristic of a first-order magnetostrutural transition, from an antiferromagnetic state to a ferromagnetic state, at the critical temperature TN, being TN close to the room temperature. This critical temperature is strongly dependent on the external magnetic applied field, the pressure, and the composition of the alloy, among others parameters. Recent studies show that, due to its high magnetocaloric effect, this material is a good candidate for applications in magnetic refrigeration. Also, heterogeneous magnets based on FeRh present remanence and coercivity enhancement, characteristics that become it a potential exchange-spring magnet. The proposed project considers the preparation, structural characterization and study of the magnetic properties of nanocrystalline powders of FeRh, FeRh+a-Fe and FeRh+Ni obtained by mechanical alloying in high energy mills; FeRh, FeRh/a-Fe, FeRh/Py, FeRh/SmCo, FeRh/CoPd thin films prepared via sputtering; and films and nanowires of FeRh, electroplated in templates of alumina and polycarbonate nanopourous membranes. The study of dimensionality effects on the antiferro-ferromagnetic transition; exchange-bias and exchange-spring magnets properties in heterogeneous systems based on FeRh alloy; and of the dynamic response of these systems, especially magnetoresistance, will be emphasized. (AU)