Changes in cluster magnetism and suppression of local superconductivity in amorphous FeCrB alloy irradiated by Ar+ ions

Abstract We show that сluster magnetism in ferromagnetic amorphous Fe 67 Cr 18 B 15 alloy is related to the presence of large, D =150–250 A, α- ( Fe Cr ) clusters responsible for basic changes in cluster magnetism, small, D =30–100 A, α -( Fe, Cr ) and Fe 3 B clusters and subcluster atomic α -( Fe, Cr, B ) groupings, D =10–20 A, in disordered intercluster medium. For initial sample and irradiated one ( Φ =1.5×10 18  ions/cm 2 ) superconductivity exists in the cluster shells of metallic α-(Fe, Cr ) phase where ferromagnetism of iron is counterbalanced by antiferromagnetism of chromium. At Φ =3×10 18  ions/cm 2 , the internal stresses intensify and the process of iron and chromium phase separation, favorable for mesoscopic superconductivity, changes for inverse one promoting more homogeneous distribution of iron and chromium in the clusters as well as gigantic (twice as much) increase in density of the samples. As a result, in the cluster shells ferromagnetism is restored leading to the increase in magnetization of the sample and suppression of local superconductivity. For initial samples, the temperature dependence of resistivity ρ ( T )~ T 2 is determined by the electron scattering on quantum defects. In strongly inhomogeneous samples, after irradiation by fluence Φ =1.5×10 18  ions/cm 2 , the transition to a dependence ρ ( T )~ T 1/2 is caused by the effects of weak localization. In more homogeneous samples, at Φ =3×10 18  ions/cm 2 , a return to the dependence ρ ( T )~ T 2 is observed.