Magnetoelastic effect in R2Ni2In (R = Tb and Tm) investigated by neutron powder diffraction

Magnetoelastic effect in R2Ni2In (R = Tb, Tm), associated with the antiferro- to paramagnetic phase transition at the Neel temperature T-N equal to 40 K (R = Tb) or 4.8 K (R = Tm), has been investigated by neutron powder diffraction. Rietveld refinement reveals that the orthorhombic crystal structure, reported at room temperature, is stable down to low temperatures, including magnetically ordered state. Based on the diffraction data, thermal evolution of the lattice parameters a, b and c and the unit cell volume V have been determined. Both the lattice parameters as well as the unit cell volume show distinct jumps in the vicinity of the respective Neel temperatures, indicating presence of the magnetoelastic effect. The values of the lattice strains Delta a, Delta b, Delta c and change of the unit cell volume Delta V, associated with the antiferro- to paramagnetic phase transition, are reported.