Low temperature ferromagnetism in Rh-rich Fe-Rh granular nanowires

RIVA, J.S.; POZO-LÓPEZ, G.; CONDÓ, A.M.; FABIETTI, L.M.; URRETA, S.E.

JOURNAL OF ALLOYS AND COMPOUNDS

ELSEVIER SCIENCE SA

Año: 2018 vol. 747 p. 1008 - 1008

0925-8388

oble/transition bimetallic nanowires of nominal composition FexRh100-x (x ¼ 15, 25, 54) are AC electrodeposited into 20 nm diameter hexagonally self-assembled nanopores of anodic alumina membranes. Nanowires about 18 nm in diameter and 1 mm long are polycrystalline and, depending on composition, different crystalline phases are obtained. Iron-rich (x ¼ 54) wires are biphasic, composed by large a-Fe grains (>100 nm in length) and clusters of small (3 nm in average) grains of fcc g-Rh(Fe) phase, with composition near (30 ± 5) at% Fe. Rh-rich (x ¼ 15, 25) nanowires are formed by very small grains of gRh(Fe) phase. Grain size depends on Rh content: grains in wires with x ¼ 15 are the smallest with a mean size of (2.1 ± 0.9) nm. The low temperature magnetic properties of these small grained nanowires exhibit new features: they are all ferromagnetic at 5 K while, at room temperature wires with 54 at.% Fe and 25 at.% Fe are ferromagnetic and those with 15 at.% Fe are weakly superparamagnetic