New Sequences of Phase Transition in Ni-Mn-Ga Ferromagnetic Shape Memory Nanoparticles

Abstract

In-situ high-energy X-ray diffraction was used for tracing the structural transitions in Ni 2 MnGa and Ni 47 Mn 25 Ga 22 Co 6 nanoparticles that were prepared by a ball-milling and subsequent annealing process. A decrease in martensitic transformation temperature was evidenced in all annealed nanoparticles. It was found that a three-layered modulated structure, usually observed as a metastable premartensitic phase in coarsegrained alloys, becomes a stable phase in the annealed Ni 2 MnGa nanoparticles up to 4 K.

Investigation of the structural, electronic, transport and magnetic properties of Co2FeGa Heusler alloy nanoparticles

“…However, the presence of some degree of structural disorder in these materials strongly reduces these properties while higher degree of ordering (L2 1 /B2) stabelizes the spin polarization [12,13]. For developing next generation of spin related and ferromagnetic shape memory devices, the understanding of the physical properties of Heusler alloys at the nanoscale is of vital importance and will play a decisive role [14][15][16].…”

Internal stress dependent structural transition in ferromagnetic Ni–Mn–Ga nanoparticles prepared by ball milling

“…This reveals that peaks become sharp with reduction in FWHM when annealed to higher temperatures. Post-annealing at 873 K of the ball milled sample recovers the structural property to that of the bulk state Heusler phase with peak shift towards higher angles, suggesting a decrease in cell volume [13,26,28,29].…”

Structural Transitions and Magnetic Properties of Ni50Mn36.7In13.3 Particles with Amorphous-Like Phase

“…To overcome this problem, and driven by the motivation to design new types of functional materials used as nanoscale actuators, Wang and co-workers [12,13] have prepared Ni-Mn-Ga nanoparticles through the highenergy ball-milling method. It is found that the Ni-MnGa nanoparticles prepared by ball milling showed a disordered face-centered-cubic structure, which transformed back to the ordered Heusler structure upon annealing.…”

“…The annealed Ni-Mn-Ga nanoparticles undergo new sequences of martensitic structural transitions, different from their coarse-grained counterparts. [12,13] Actually, high-energy ball milling provides an effective routine in synthesizing a variety of alloy phases with the equilibrium or nonequilibrium state. For different intermetallic compounds with a variety of ordered atomic arrangements, the ball-milling process can induce amorphous particles, nanostructured particles, metastable crystalline, quasi-crystalline particles, etc.…”

“…For different intermetallic compounds with a variety of ordered atomic arrangements, the ball-milling process can induce amorphous particles, nanostructured particles, metastable crystalline, quasi-crystalline particles, etc. [12][13][14][15][16][17][18][19][20][21][22] Zhou and Bakker [18,19] reported that both ordered Co 2 Ge and GdAl 2 are ferromagnets at lower temperatures. After ball milling, Co 2 Ge eventually transforms to the amorphous state, [18] while GdAl 2 disorders atomically but remains crystalline.…”