Observation of inverted hysteresis loop and thermomagnetic irreversibility in the antiferromagnetic Mn5Si3 alloy

Abstract

The structural and magnetic behavior of Mn-site doped intermetallic manganese silicide alloys of nominal compositions Mn5−xAxSi3 (x = 0.05, 0.1, 0.2 and A = Ni, Cr) have been investigated with a focus to the inverted hysteresis behavior and thermomagnetic irreversibility. Room temperature x-ray powder diffraction data confirm that all the doped alloys crystallize in hexagonal D88 type structure with space group P 63/mcm. The doped alloys are found to show paramagnetic (PM) -collinear antiferromagnetic (AFM2) -noncollinear antiferromagnetic (AFM1) transitions during cooling from room temperature. A significant decrease in the critical values of both AFM1-AFM2 transition temperatures and fields have been observed with the increasing Ni/Cr concentration. Inverted hysteresis loop, field-induced arrest, and thermomagnetic arrest, the key features of the undoped Mn5Si3 alloy, are found to be significantly affected by the Mn-site doping and eventually vanishes with 4% doping.

Complex magnetic structure and spin waves of the noncollinear antiferromagnet Mn5Si3

“…Finally, a third phase transition takes place (labeled as C in Fig. 6) at ∼ 6.4 T. This phase relates to the experimentally reported field-induced AFM2 phase 8,9,12,21 and occurs at about 9.5 T at 10 K (see Fig. 2).…”

“…2. A very steep phase boundary T N2 (B) is outlined between the AFM2 phase and the PM state and in the temperature range where the AFM2 phase is observed, no field-induced transition is reported up to the maximum investigated field of 10 T. Below 60 K, the increasing magnetic field precipitates transitions from the AFM1 phase to another intermediate AFM phase 9,12 (marked as AFM1' in Fig. 2) before reaching the collinear AFM2 phase.…”

“…Mn 5 Si 3 is another Mn-based metallic antiferromagnet (AFM) that has lately regained scientific interest owing to interesting thermodynamic (inverse magnetocaloric effect 7,8 , inverted hysteresis loop, and thermomagnetic irreversibility 9 ) and transport (large anomalous Hall ef-fect 10 ) phenomena. It has two stable AFM phases, namely the AFM2 for 60 < T < 100 K and the AFM1 for T < 60 K, that are confirmed by a plethora of macroscopic measurements 7,[9][10][11][12][13] in thin film, polycrystalline and single crystal samples.…”

“…Mn 5 Si 3 is another Mn-based metallic antiferromagnet (AFM) that has lately regained scientific interest owing to interesting thermodynamic (inverse magnetocaloric effect 7,8 , inverted hysteresis loop, and thermomagnetic irreversibility 9 ) and transport (large anomalous Hall ef-fect 10 ) phenomena. It has two stable AFM phases, namely the AFM2 for 60 < T < 100 K and the AFM1 for T < 60 K, that are confirmed by a plethora of macroscopic measurements 7,[9][10][11][12][13] in thin film, polycrystalline and single crystal samples. While neutron diffraction studies in powders 14 and single crystals 15 are in agreement regarding the collinear spin arrangement in the AFM2 phase, in the past years several contradicting spin structures 14,[16][17][18] have been proposed for the noncollinear AFM1 phase, where the interesting thermodynamic and transport properties are observed.…”

“…Despite the controversy regarding the spin orientation in the AFM1 phase, it is accepted that not only two-thirds of the Mn2 (as in the AFM2 phase) but also the Mn1 atoms carry a magnetic moment leaving still one-third of the Mn2 atoms without moment 14,16,18 . In Mn 5 Si 3 , apart form the reduction of temperature, the application of an external magnetic field results in field-induced transitions 9,11,12,23 . The magnetic phase diagram as a function of temperature and magnetic field as established by magnetization and electrical transport measurements is shown in Fig.…”