Magnetic and structural properties of the magnetic shape memory compound Ni₂Mn_1.48Sb_0.52

Abstract

Magnetization and high resolution neutron powder diffraction measurements on the magnetic shape memory compound Ni(2)Mn(1.48)Sb(0.52) have confirmed that it is ferromagnetic below 350 K and undergoes a structural phase transition at T(M)≈310 K. The high temperature phase has the cubic L2(1) structure with a = 5.958 Å, with the excess manganese atoms occupying the 4(b) Sb sites. In the cubic phase above ≈310 K the manganese moments are ferromagnetically aligned. The magnetic moment at the 4(a) site is 1.57(12) μ(B) and it is almost zero (0.15(9) μ(B)) at the 4(b) site. The low temperature orthorhombic phase which is only fully established below 50 K has the space group Pmma with a cell related to the cubic one by a Bain transformation a(orth) = (a(cub) + b(cub))/2; b(orth) = c(cub) and c(orth) = (a(cub) - b(cub)). The change in cell volume is ≈2.5%. The spontaneous magnetization of samples cooled in fields less than 0.5 T decreases at temperatures below T(M) and at 2 K the magnetic moment per formula unit in fields up to 5.5 T is 2.01(5) μ(B). Neutron diffraction patterns obtained below ≈132 K gave evidence for a weak incommensurate magnetic modulation with propagation vector (2/3, 1/3, 0).

Isothermal section of the Ni–Mn–In ternary system at 773 K

“…All of these properties originate from the magnetic field-induced structural transformation from a high temperature high symmetry cubic structure (ferromagnetic austenite) to a low temperature orthorhombic structure (paramagnetic/antiferromagnetic martensite) with lesser crystal symmetry [8][9][10][11], which offers the possibility of application in high-performance actuators [12], environmentfriendly magnetic refrigerators [13], etc. The martensitic transformation temperatures of these alloys are drastically decreased by application of a magnetic field and magnetic-field-induced reverse transformation, namely, metamagnetic phase transition, occurs near the martensitic reverse transformation start temperature Ms [14,15].…”

Structural and magnetic properties probed using neutron diffraction technique in Ni50−xCoxMn38Sb12 (x=0 and 5) Heusler system

“…Recently in certain full Heusler systems, neutron diffraction technique has been utilized to unravel the crystal and magnetic structures [17][18][19][20][21][22]. By virtue of their magnetic moments, neutrons undergo scattering from the magnetic moments, in addition to the nuclear scattering.…”

“…In the case of Heusler alloys, neutron diffraction studies have been utilized in various NiMn based alloys [17,18]. In a recent neutron diffraction study in NiMnSn and NiMnSb, the structural transition from high temperature cubic L2 1 phase to low temperature orthorhombic phase (Pmma) has been established [19,20].…”

Constitutive modelling of magnetic shape memory alloys with discrete and continuous symmetries

“…In the present case, the NiMnCoIn crystal exhibits L2 1 -type Heusler structure with the Fm3m space group [39]. The magnetic point group has not been reported to date.…”