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.