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


Moya X. , GONZALEZ-ALONSO D., MANOSA L., PLANES A., Garlea V. O. , Lograsso T. A. , ...Daha Fazla

PHYSICAL REVIEW B, cilt.79, 2009 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

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 on 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) approximate to 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' = (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 (1) over bar0 > directions. Additionally, we measured low-lying phonon-dispersion branches and elastic constants in applied magnetic fields aimed to characterize the magnetoelastic coupling.