Magnetic percolation and inequivalence of Fe sites in YFexCo2−x (x = 0.03 and 1) Laves phase compounds

Abstract

YCo2 compound is an exchange-enhanced Pauli paramagnet on the verge of being magnetic. Topological or chemical disorder can induce in it ferromagnetic long-range ordering. The influence of Fe substitution and quenched-in topological disorder on the magnetic properties of YFe0.03Co1.97 and YFeCo is studied. Structural and magnetic properties of these compounds are analyzed by means of X-ray diffraction, vibrating sample magnetometry, Mössbauer spectroscopy and AC magnetic susceptibility measurements. All samples crystallize in cubic MgCu2-type phase with lattice constant changing from 7.223 Å for YCo2 through 7.221 Å for YFe0.03Co1.97 to 7.313 Å for YFeCo. Fe atoms are responsible for stabilization of magnetic moments on Co, and mictomagnetism is observed in YFe0.03Co1.97 sample. Upon further substitution, as in YFeCo, long-range ordering appears. The Mössbauer spectra permitted distinction between two magnetically inequivalent Fe sites, as reported earlier for YFe2.