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

Abstract

The high-energy ball-milling method was used for fabricating Ni 50 Mn 36.7 In 13.3 fine-sized particles. The as-melt polycrystalline Ni 50 Mn 36.7 In 13.3 alloy exhibits a 14 M modulated martensite structure at room temperature (RT). The atomic pair distribution function analysis together with the differential scanning calorimetry technique proved that the 14 M modulated martensite transformed to a metastable amorphous-like structure after ball milling for 8 hours. Annealing of the ball-milled particles with the amorphous-like phase first led to the crystallization to form a B2 structure at 523 K (250°C), and then an ordered Heusler L2 1 structure (with a small tetragonal distortion) at 684 K (411°C). The annealed particles undergo different structural transitions during cooling, tailored by the atomic arrangements of the high-temperature phase. Low-field thermomagnetization measurements show that the ball-milled particles with the amorphous-like structure or the atomically disordered crystalline structure exhibit a magnetic transition from the paramagnetic-like to the spin-glass state with decreasing temperature, whereas the crystalline particles with the ordered Heusler L2 1 structure present a ferromagnetic behavior with the Curie temperature T c % 310 K (37°C).

Crystallization Kinetics and Structure Evolution during Annealing of Ni-Co-Mn-In Powders Obtained by Mechanical Alloying

“…The significant broadening of the main reflection (at approximately 43° 2θ— Figure 2 ) indicates that the as-milled powder consists of a mixture of amorphous (or strongly refined nanocrystalline—peak 1) and bcc (peak 2) which have been identified as “the amorphous-like phase” [ 23 , 25 ].…”

“…It is due to the lattice distortion of the parent phase and L2 1 growth. Liu et al [ 23 ] observed a tetragonally distorted Heusler phase in Ni 50 Mn 36.7 In 13.3 powders annealed for 30 min at 411 °C (684 K). The activation energies (E a ) determined for studied Ni 45.5 Co 4.5 Mn 36.6 In 13.4 MA alloys are similar to those observed for other magnetic shape memory powders obtained by high-energy-ball-milling (e.g., Ni-Mn-Ga and Ni-Mn-In) and slightly higher than for NiMn-based films obtained by magnetron sputtering.…”

“…During heating of the ball-milled powders, they also observed the structural transition from fcc to bcc [ 21 ]. For the Ni 50 Mn 34 In 16 powder, Sánchez-Alarcos [ 22 ] recorded a two-step transition from an “amorphous-like” phase to the B2-ordered structure, whereas Liu et al, for the same system (Ni 50 Mn 36.7 In 13.3 powders produced by high-energy ball milling), showed the one-step transition from the amorphous phase to B2, followed by the L2 1 ordered structure [ 23 ].…”

Low temperature magnetic properties of a Ni50Mn34In16 ball-milled metamagnetic shape memory alloy

“…The previous results, which allow to control the microstructure of the alloy and its influence on the magnetic behavior, are in full agreement with behaviors observed in similar alloy systems. Nevertheless, the possible spin glass behavior linked to the amorphous state (proposed in a similar Ni-Mn-In alloy [26]) and the evolution of magnetism brought by the crystallization process needs to be analyzed in more detail. In this sense, magnetization and susceptibility measurements has been performed on the milled samples.…”

“…For the case of the metamagnetic alloys, this effect has been scarcely analyzed in the bibliography. As in NiMnGa powders, the austenitic phase is obtained only after heating up to high temperatures in NiMnSn (1223 K) [25] and NiMnIn particles (673 K) [26]. In this latter case, a magnetic transition from paramagnetic-like to spin-glass state is suggested to occur at low temperatures as a consequence of the induced defects.…”