Metamagnetic behavior in L10-MnAl synthesized by the post annealing of electrodeposited MnAl powder

Abstract

The effect of annealing temperature on MnAl alloy powder synthesized by electrodeposition method was investigated. Single L10-MnAl (τ-phase) with nearly stoichiometric composition was obtained by electrodeposition method. In annealed at 400°C sample coercivity of 12.3 kOe was observed. And by annealing at 450–550°C, metamagnetic behavior was observed. In these samples, the main phase was τ-phase although weak peaks of low-temperature Al-rich γ2 phase appeared. The order parameter S of the τ-phase exhibited a peak value with variation of the annealing temperature. The peak value was 0.90 at an annealing temperature of 500°C, where the metamagnetic behavior was most clearly observed. This indicates that the nearly perfectly ordered τ-phase shows metamagnetism and the Mn atoms occupying the Al sites play an important role in the metamagnetism of the τ-phase.

Antiferromagnetism in perfectly ordered L10-MnAl with stoichiometric composition and its mechanism

“…However, the 600 °C-annealed sample shows ferromagnetic behaviour with smaller coercivity than that of the as-deposited one. The magnetism of electrodeposited MnAl powder drastically changes by annealing, which has already been reported in previous article 17 .

Figure 1 ( a ) Dependence of magnetization curves on annealing condition.

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“…1 in Ref. 17 ; licensed under a Creative Commons Attribution (CC BY) license. ( b ), Temperature-dependent magnetizations of the annealed at 550 °C sample.…”

“…Recently we have reported that a τ-phase with nearly stoichiometric composition with higher-ordering parameter was obtained by post-annealing of electrodeposited MnAl powder, but it unexpectedly showed metamagnetism 17 . However, the mechanism of metamagnetism is unclear, and it may reflect exhibiting antiferromagnetic ground state.…”

Structural, magnetic and magneto-optical studies of Mn/Al bilayer thin films on GaAs substrates

“…The ferromagnetic s-phase of MnAl is typically achieved by controlled the cooling of the 3-phase or by quenching followed by annealing at 300-550 C. 25 On further increasing the temperature from 550 C to 600 C, the s-phase decomposed into non-magnetic g and b phases. 26,27 Previous studies revealed that ferromagnetic ordering was enhanced in the MnAl thin lms on increasing the annealing temperature to 500 C. 27,28 Therefore, we selected the temperature range from 300 to 500 C to achieve the desired ferromagnetic phase. Our results are consistent with previous studies 25,27,28 and suggest the enhancement of the ferromagnetic s-phase in MnAl thin lm up to the annealing temperature of 500 C. Annealing above 500 C was not performed in this study because of the reduction in the ferromagnetic s-phase as already reported for annealing temperatures $ 550 C. 26,27 The XRD patterns for MnAl_400_1h and MnAl_400_2h lms annealed for different times are shown in Fig.…”

“…Our study revealed that increasing the annealing time might lead to the reduction of the ferromagnetic s-phase, which is consistent with previous studies. 14,27 The inset pictures in Fig. 6 show the hysteresis curves plotted at a lower scale.…”