Magnetostrictive properties of Tb0.2Gd0.8 single crystal in high magnetic fields

•The magnetostrictions of Tb0.2Gd08 single crystal were measured up to 14 T.•The giant linear and volume magnetostriction was found in Tb0.2Gd0.8 single crystal.•The magnetostriction constants of Tb0.2Gd08 single crystal were determined.•At low temperatures the magnetostriction is caused MCA and exchange interactions.•Two-ion exchange interaction is responsible for the giant magnetostriction at TC. Temperature and field dependencies of the magnetostriction of the Tb0.2Gd0.8 single crystal were measured in strong magnetic fields up to 14 T in a temperature range of 4.2–300 K. The temperature dependencies of five magnetostriction constants λ1α,0, λ2α,0, λ1α,2, λ2α,2 and λγ,2 were determined, using Clark's theory for rare-earth hexagonal close-packed single crystals. Giant values of linear and volume magnetostriction due to forced magnetostriction were found in the Tb0.2Gd0.8 single crystal (λbc = 1.6 × 10−3) in the region of the Curie temperature (near room temperatures). It is shown that giant values of forced magnetostriction are caused by the sharp dependence of exchange interactions on interatomic distances along the hexagonal the c axis.