Pressure effect on magnetic moments in ordered Ni₃Mn and disordered Ni_100−xMn_xalloys:ab initiocalculation and experiment

Abstract

We have revealed a substantial difference in the pressure behavior of magnetization of the ordered Ni 3 Mn and the disordered Ni 75 Mn 25 and Ni 80 Mn 20 alloys in the pressure range up to 1.2 GPa. To explain in detail the peculiarities of magnetic properties of the Ni-rich NiMn alloys, the reference electronic structure of the alloys was calculated using the tight-binding linear muffin-tin orbital approach. The effect of disorder was described by the coherent potential approximation. The theoretical ab initio calculations (with changes of the lattice parameters up to 1%) elucidated the pressure stability of the magnetic Mn moments and revealed that the very pronounced decrease in the magnetization of the disordered alloys under pressure is caused by the relatively small change in portion of the Mn moments with parallel and anti-parallel orientation with respect to the total moment. The quantitative agreement with experiment has been reached for the pressure parameters d ln M/dP .

Combined effect of magnetic field and hydrostatic pressure on the phase transitions exhibited by Ni-Mn-In metamagnetic shape memory alloy

“…A similar slope has been reported in other NiMn-based Heusler compounds [36]. A considerable decrement of the M max (P) dependence can be explained within a model of the uncompensated local moment disorder proposed for Kamarad et al [48] for NiMn-based MetaMSMAs. This model illustrates a high sensitivity of the total magnetization to the atomic order and the external pressure.…”

“…It demonstrated that the Mn-Mn exchange interaction within the first and fourth coordination spheres can change sign when the applied pressure diminishes the Mn-Mn distance to 0.34 nm, but the pressure required is quite high. On the other hand, disorder and defects, giving rise to atomic interchanges between Ni and Mn sublattices [48] increase the influence of pressure on the magnetic properties of Ni-Mn-Sn alloy [36], as suggested by the dependence of the magnetic properties of MetaMSMAs on the thermal treatments [40]. It should be also stressed, that ZFC and FC magnetisation curves are entirely different in the temperature interval of FMM state (see Fig.…”

“…Particularly, values of the parameter dlnM max /dP, equal to -8•10 -3 GPa -1 and -38•10 -3 GPa -1 , have been determined for the ordered and disordered Ni 3 Mn alloys, respectively, showing a high impact of the atomic disorder on this parameter [48]. The enhanced value of dlnM max /dP obtained in this work is indicative of a certain degree of disorder related to the high Mn content and, as a result, the presence of antiferromagnetic coupling due to the reduction of the Mn-Mn distances.…”

Effect of pressure and high magnetic field on phase transitions and magnetic properties of Ni1.92Mn1.56Sn0.52 and Ni2MnSn Heusler compounds

“…Magnetization decreases with fig.6. The low value of magnetization of martensite and its relatively fast decrease with pressure at low temperature is in agreement with the model of uncompensated disorder local moment (uDLM) proposed for the Ni-Mn-based alloys in[28]. In the studied Mn-rich compound, magnetic moment of the surplus Mn atoms at the lattice positions of Sn can be turned to antiparallel direction with respect to the Mn moments in the proper lattice positions due to the antiferromagnetic Mn-Mn interaction induced by the shorter Mn-Mn interatomic distances.…”

Pressure-Induced Increase of the Total Magnetic Moment in Ferrimagnetic Ni_1.9375Mn_1.5625Sn_0.5 Martensite: A Quantum-Mechanical Study

“…encyclopedia 54) and references therein. This effect was reported in numerous systems, such as body-centered-cubic iron, 55) binary MnGe system, 56) Gd 2 Fe 17 intermetallic compound, 57) or both ordered Ni 3 Mn and disordered NiMn alloys, 58) to name just a few prominent examples. Therefore, to identify the origin of the present anomalous trend, that we identified, we thoroughly analyze magnetic properties of Ni 1.9375 Mn 1.5625 Sn 0.5 below.…”