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Interplay between localized and itinerant magnetism in Co-substituted FeGa 3

2014; American Physical Society; Volume: 89; Issue: 10 Linguagem: Inglês

10.1103/physrevb.89.104426

1550-235X

A.A. Gippius, Valeriy Yu. Verchenko, A. V. Tkachev, N.E. Gervits, C. S. Lue, Alexander A. Tsirlin, N. Büttgen, Wolfgang Krätschmer, M. Baenitz, Michael Shatruk, Аndrei V. Shevelkov,

Magnetic Properties of Alloys

The evolution of the electronic structure and magnetic properties with Co substitution for Fe in the solid solution Fe${}_{1\ensuremath{-}x}$Co${}_{x}$Ga${}_{3}$ was studied by means of ab initio band-structure calculations and nuclear spin-lattice relaxation $1/{T}_{1}$ of the ${}^{69,71}$Ga 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 FeGa${}_{3}$, the temperature dependence of the ${}^{69}(1/{T}_{1})$ exhibits a huge maximum at about $T\ensuremath{\sim}6$ K indicating the existence of in-gap states. The opposite binary compound, CoGa${}_{3}$, demonstrates a metallic Korringa behavior with $1/{T}_{1}\ensuremath{\propto}T$. In Fe${}_{0.5}$Co${}_{0.5}$Ga${}_{3}$, the relaxation is strongly enhanced due to spin fluctuations and follows $1/{T}_{1}\ensuremath{\propto}{T}^{1/2}$, 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 ${\ensuremath{\mu}}_{B}$/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.