Lattice dynamics in magnetic superelastic Ni-Mn-In alloys. Neutron scattering and ultrasonic experiments

Abstract

Neutron scattering and ultrasonic methods have been used to study the lattice dynamics of two single crystals of Ni-Mn-In Heusler alloys close to Ni${}_{50}$Mn${}_{34}$In${}_{16}$ magnetic superelastic composition. The paper reports the experimental determination of the low-lying phonon dispersion curves and the elastic constants for this alloy system. We found that the frequencies of the TA${}_2$ branch are relatively low and it exhibits a small dip anomaly at a wave number ${\xi }_0\approx 1/3$, which softens with decreasing temperature. Associated with the softening of this phonon, we also observed the softening of the shear elastic constant $C^{\prime }=(C_{11}-C_{12})/2$. Both temperature softenings are typical for bcc based solids which undergo martensitic transformations and reflect the dynamical instability of the cubic lattice against shearing of $\{110\}$ planes along $<1\bar{1}0>$ directions. Additionally, we measured low-lying phonon dispersion branches and elastic constants in applied magnetic fields aimed to characterize the magnetoelastic coupling.

8 pages, 7 figures. Accepted for publication in the Physical Review B

References in corpus (4)

• Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In
• Cooling and heating by adiabatic magnetization in the Ni${}_{50}$Mn${}_{34}$In${}_{16}$ magnetic shape memory alloy
• Lattice dynamics and phonon softening in Ni-Mn-Al Heusler alloys
• Temperature and magnetic field dependences of the elastic constants of Ni-Mn-Al magnetic Heusler alloys

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• Strain behavior and lattice dynamics in Ni50Mn35In15
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