Impact of Co and Fe Doping on the Martensitic Transformation and the Magnetic Properties in Ni‐Mn‐Based Heusler Alloys

Abstract

Doping with Co and Fe is a promising strategy to enhance the performance of Ni-Mn-based magnetocaloric materials. We investigate here the impact of these two elements on the magnetic properties and the martensitic transformations in Mn-rich Ni-Mn-Al Heusler alloy. Based on ab initio ground-state energies, we explain the martensitic transformation temperatures in these alloys. The magnetic ground states of the austenite and the martensite phases are discussed on the basis of magnetic exchange parameters. A thorough comparison of the transition temperatures and the change in saturation moments during martensitic transformation brings into light the relative potential of the two substitutional elements for future applications.

Hysteresis Design of Magnetocaloric Materials—From Basic Mechanisms to Applications

“…Considerable interactions are also found among the Co atoms on all sites and with Ni, whereas Ni–Ni interactions are negligible. Similar mechanisms stabilizing FM order have already been pointed out in other first‐principles studies of quaternary Ni–Mn–(Al, Ga, In)–Co Heusler alloys . In the martensite phase, the interactions involving Co X show a very similar reduction upon the transition to martensite compared to Ni, which is also located on the X‐sites.…”

Coupling Phenomena in Magnetocaloric Materials

“… Calculated magnetic exchange parameters as a function of distance between the host Mn and the rest of the atoms in units of the lattice constant a for cubic austenite (a, b) and tetragonal martensite (c, d) …”

“…The EMTO‐CPA (shifted) results denoted by smaller open circles refer to EMTO‐CPA computed values after being shifted down by 26 meV per formula unit (f.u.) so that the result for Ni 50 Mn 37.5 Al 12.5 is aligned with the corresponding VASP computed value …”

Magnetocaloric and Elastocaloric Effects in All‐d‐Metal Ni37Co9Fe4Mn35Ti15 Magnetic Shape Memory Alloy

“…The Fe‐doping in some Heusler alloys could also modify the magnetic structure of the austenite phase with FM being the preferred state . However, Co substituted by Fe will weaken the FM exchange interaction in some Heusler alloys due to the relatively weak interactions between Mn and Fe . At the same time, the substitution Co with Fe plays a critical role in tuning MT temperature due to the change in the number of valence electrons …”