Magnetic-field-induced shape recovery by reverse phase transformation

Abstract

Large magnetic-field-induced strains have been observed in Heusler alloys with a body-centred cubic ordered structure and have been explained by the rearrangement of martensite structural variants due to an external magnetic field. These materials have attracted considerable attention as potential magnetic actuator materials. Here we report the magnetic-field-induced shape recovery of a compressively deformed NiCoMnIn alloy. Stresses of over 100 MPa are generated in the material on the application of a magnetic field of 70 kOe; such stress levels are approximately 50 times larger than that generated in a previous ferromagnetic shape-memory alloy. We observed 3 per cent deformation and almost full recovery of the original shape of the alloy. We attribute this deformation behaviour to a reverse transformation from the antiferromagnetic (or paramagnetic) martensitic to the ferromagnetic parent phase at 298 K in the Ni45Co5Mn36.7In13.3 single crystal.

Stable magnetostructural coupling with tunable magnetoresponsive effects in hexagonal ferromagnets

“…These magnetoelastic transitions have been utilized in the intensive investigations of a large body of giant magnetocaloric materials [19][20][21][22][23][24][25][26][27] . In contrast, in typical FMMTs, the change of structural symmetries of austenite and martensite is remarkable [6][7][8][9][10][11] . The transition converts the different magnetic states (moment values and type of coupling) in between the two phases that have separate Curie (Néel) temperatures.…”

“…T he ferromagnetic martensitic transition (FMMT) [1][2][3] , a coinciding crystallographic and magnetic transition mainly found in Fe-based and Heusler ferromagnetic alloys, is receiving increasing attention from both the magnetism and the material science community due to the massive variations of associated magnetoresponsive effects, such as magnetic-field-induced shape memory/strain effect [4][5][6][7] , magnetoresistance 8,9 , Hall effect 10 and magnetocaloric effect 11,12 . These effects are of interest for many potential technological applications like magnetic actuators 13,14 , sensors 15 , energy-harvesting devices 16 and solid-state magnetic refrigeration 17 .…”

Magnetic entropy change involving martensitic transition in NiMn-based Heusler alloys

“…[47]. This means that the martensitic transformation in the present Ni 45 Co 5 Mn 36.5 In 13.5 is easier to drive by a magnetic field.…”

“…The huge FM shape memory effect recently discovered in metamagnetic alloys with exact compositions Ni 45 Co 5 Mn 50−x In x (x = 13.3, 13.4, 13.5) [47,48] warrants further experimental and theoretical study. The introduction of Co atoms in metamagnetic alloys enhances the Zeeman energy µ 0 ∆M · H through enlarging the magnetization difference across the martensitic transformation; thus an extremely large stress can be generated by a magnetic field.…”

“…[47,48] In these Ga-free Ni-Mn-Z Heusler alloys, where Z can be a group III or IV element such as In, Sn, or Sb, the excess of Mn causes a fundamental change of magnetism between the parent and the product phases. As the Mn content exceeds the ratio 2:1:1 in Ni:Mn:Z, the nearest Mn-Mn neighbors are introduced, which usually gives rise to antiferromagnetic (AFM) coupling.…”