Rapidly quenched FexTa100−x alloys

Binary alloys of FexTa100−x were made by high‐rate sputtering. A sharply defined boundary separates the composition ranges in which crystalline alloys (93≤x≤100) and amorphous alloys (15≤x≤90) are formed. The amorphous alloys with Fe concentrations up to the threshold of xc≂65 are nonmagnetic. For the samples with x>xc, the magnetic ordering temperature (Tc) varies monotonically with Fe content to 200 K for a‐Fe90Ta10. However, the crystalline alloys, with slightly higher Fe content, are strongly ferromagnetic. Their Tc’s are several hundred degrees higher, accompanied by large increases in magnetic moment and hyperfine fields. This discontinuity illustrates the sensitivity with which the magnetic properties of Fe‐transition metal alloys depend on structure. In contrast, no discontinuity has been observed in Co‐Ta alloys.