An AC magnetic susceptibility study of a sigma-phase Fe65.9V34.1 alloy

• AC susceptibility study of sigma-phase Fe59V41 intermetallic compound.
• Discovery of a reentrant character of magnetism P → FM → SG
• Detailed characterization of the magnetic ground state.
• Figures of merit characteristic of canonical spin glasses.

A sigma-phase Fe65.9V34.1 alloy was investigated with the AC magnetic susceptibility as a function of temperature, frequency and external magnetic field. Evidence was found that its magnetism shows features characteristic of a reentrant behavior viz. two transitions: first at TC ∼312 K from the paramagnetic state into a collinear ferromagnetic one, and second at Tf ∼302 K to a mixed state (sometimes referred to as a ferromagnetic or re-entrant spin glass) which, finally, at a lower temperature (TRSG ∼60 K) transforms to a state where replica symmetry is broken. The frequency dependence of Tf is lower than that of canonical spin glasses, a feature that in the light of a high concentration of magnetic carriers can be understood in terms of a weak coupling between magnetic clusters.

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