Determination of the magnetic phase diagram in the H-T plane for a sigma-phase Fe ₄₇ Mo ₅₃ alloy: Double re-entrant transition

Magnetization measurements were carried out in the in field-cooled (FC) and in zero-field-cooled (ZFC) conditions versus temperature, T, and external magnetic field, H, on a sigma-phase Fe ₄₇ Mo ₅₃ compound. Analysis of the measured M _FC and M _ZFC curves yielded values of characteristic temperatures: magnetic ordering (Curie) temperature, T _C , irreversibility temperature, T _ir , temperature of the maximum in M _ZFC , T _m , identified as the Nėel (T _N ) temperature, and cross-over temperature, T _co . Based on these temperatures a magnetic phase diagram in the H-T plane was outlined. The field dependences of the characteristic temperatures viz. of the irreversibility and of the cross-over temperatures were described in terms of a power law with the exponent 0.5(1). In the whole range of H i.e. up to 800 Oe, except the one H ≤ 50 Oe, a rare double re-entrant transition viz. PM → FM → AF → SG takes place. For small fields i.e. H ≤ 50 Oe a single re-entrant transition viz. PM → FM → SG is revealed.