We report on the magnetic properties and electronic structure of ${\mathrm{Cu}}_2\mathrm{CrAl},$ and ${\mathrm{Fe}}_x\mathrm{TiSn},$ ${\mathrm{Fe}}_{2-x}{\mathrm{Ni}}_x\mathrm{TiSn},$ and ${\mathrm{Fe}}_{2-x}{\mathrm{Co}}_x\mathrm{TiSn}$ cubic solid solutions. The analysis of the magnetic susceptibility $\chi \mathrm{}\left(T\right),$ electrical resistivity $\rho \mathrm{}\left(T\right),$ and lattice thermal expansion $a\left(T\right)\mathrm{}$ data allowed us to find the existence of a thermodynamic phase transition in all samples at $\sim 240\hspace{0.5em}\mathrm{K}.$ The observed anomalies at $\sim 240\hspace{0.5em}\mathrm{K}$ provide evidence of an isostructural phase transition which could be created by a large strain due to a small size of grains. ${\mathrm{Fe}}_2\mathrm{TiSn}$ was observed by high-resolution electron microscopy to be composed of nanosized solid solution grains of the order of 100 nm. We discuss the superparamagnetic behavior in these alloys which results from an atomic disorder.

• Received 25 July 2001

DOI:https://doi.org/10.1103/PhysRevB.65.144430