Effect of the heat treatment on the electrical resistivity and magnetization reversal behavior of MnAl alloys

•The four-point method was used in conductivity measurements of MnAl alloys.•The magnetization reversal behavior of MnAl alloys was analyzed.•The effect of the ordering on the magnetic behavior in MnAl alloys was studied. The casting Mn51Al47C2 alloy were undergone two distinct heat treatment processes, consisting of the heat treatment at 1000 and 925 °C. The process followed by quenching and annealing at 500 °C for 15 min. The low electrical resistivity for the heat treatment stage at 1000 °C (165* 10-4 Ω.m) can be described by the small fraction of the L10-ordered τ-phase (40 %). But the high resistivity for heat treatment at 925 °C (290.4* 10-4 Ω.m) originates within the large fraction (>95%) of the L10-ordered τ-phase with space inversion symmetry inhibiting the transport process. The magnetic characterization revealed higher Ms, Mr and Hc along with superior (BH)max for Mn51Al47C2 alloy heat-treated at 925 °C. Additionally, the derivative hysteresis loops assign narrow maxima to Mn51Al47C2 alloy when containing less amount of the L10-ordered τ-phase. Also, tracking the magnetization reversal behavior through the Henkel plots display the increasing negative-peak dominated curve for Mn51Al47C2 alloy when moving from the as homogenized sample (100% τ-phase) to those heat-treated at 1000 (40% L10-ordered τ-phase) and 925 °C (>95% L10-ordered τ-phase), respectively. This highlights the deterioration of the exchange coupling interaction between the grains when dominated with a highly ordered L10-τ-phase. The trend is best confirmed by the quantitative results gained from recoil loops for demagnetization, reversible and irreversible magnetization curves, indicative of a low degree of exchange interactions when the L10-ordered τ-phase is dominant. Furthermore, analyzing the nucleation field through the Kondürsky model gives a low value of 0.41 kOe for the alloy in the as homogenized state. This behavior can be attributed to the boosted propagation of the anisotropy field and enhanced magnetic exchange coupling in a structure with dominant regular τ-phase for which the deleterious effects of the interfaces for the L10-ordered τ-phase can be avoided.