Tailored Magnetostructural Transitions*

Dominance of the surface atoms over the bulk atoms in nanoscaled magnetostructural systems may alter the ground state of the system and thereby change the transition character. Creation of a nanostructured magnetostuctural system was carried out via rapid solidification of (FeRh)$_{5}$Cu$_{95}$ to precipitate nanoscaled isolated FeRh precipitates in a Cu matrix upon annealing. Bulk FeRh has an abrupt antiferromagnetic - ferromagnetic transition around T =370 K. X-ray diffraction performed on the quenched (FeRh)$_{5}$Cu$_{95}$ alloy indicates only the presence of Cu of slightly expanded lattice parameter a=3.62 {\AA}, with ferromagnetism confirmed at room temperature by SQUID magnetometry. Vacuum annealing at 200 $^{\circ}$C causes a secondary phase to appear with an abrupt magnetic phase transition at T$_{t}$ = 130 K. Details of the magnetic behavior of this nanostuctured phase will be discussed.