Spin fluctuation and quantum phase transition in off stoichiometric Nb_(1-y)Fe_(2+y) alloys - Bulk magnetization and hyperfine field measurements

摘要

We report the magnetic behavior of Nb_(1-y),Fe_(2+y) (y = -0.05,-0.015, 0.0,0.03) alloys studied through measurements of bulk magnetization and local hyperfine field of ~(100)Rh probe, implanted into the samples. Both bulk and the local probe studies reveal composition driven ferromagnetic ordering, with Curie temperature T_c showing a minimum around y = -0.015, corroborating the quantum critical behavior, reported earlier. As an interesting feature, we observe that the hyperfine coupling constant obtained from the correlation of high temperature bulk magnetic susceptibility and Knight shift data also exhibits a peak near y = -0.015, reflecting a significant change in Fe-3d hybridization with ligand electrons. We believe that chemically induced change in hybridization strength plays a major role in the evolution of quantum phase transition in Nb_(1-y)Fe_(2+y) alloys.