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Abstract:
The evolution of the electronic structure and magnetic properties with
Co substitution for Fe in the solid solution Fe-1 xCoxGa3 was studied by
means of ab initio band-structure calculations and nuclear spin-lattice
relaxation 1/T1 of the (69),Ga-71 nuclei. The (69,71)(1/T-1) was studied
as a function of temperature in a wide temperature range of 2-300 K for
the concentrations x = 0.0, 0.5, and 1.0. In the parent semiconducting
compound FeGa3, the temperature dependence of the (69)(1/T1) exhibits a
huge maximum at about T similar to 6 K indicating the existence of
in-gap states. The opposite binary compound, CoGa3, demonstrates a
metallic Korringa behavior with 1/T1. T. In Fe0.5Co0.5Ga3, the
relaxation is strongly enhanced due to spin fluctuations and follows
1/T1 proportional to T1/2, which is a unique feature of weakly and
nearly antiferromagnetic metals. This itinerant antiferromagnetic
behavior contrasts with ab initio band-structure calculations, where a
ferromagnetic state with an ordered moment of 0.5 mu(B)/f.u. is
predicted. The results are discussed in terms of the interplay between
the localized and itinerant magnetism including in-gap states and spin
fluctuations.
