Giant room-temperature magnetostrictions in TbFe2 and DyFe2

Huge magnetically induced strains (∼0.2%) were observed in cubic TbFe₂ at room temperature. An anomalous "positive" temperature dependence for the magnetostriction is found for DyFe₂, yielding a peak in the magnetostriction exceeding 600 × 10⁻⁶ above room temperature. The source of the magnetostriction is the large strain-dependent anisotropy of the rare-earth ion situated at the cubic sites in the RFe₂ lattice. The magnetoelastic energy of the rare-earth ions in these compounds is estimated to be 2 to 5 times larger than that of the rare-earth elements themselves.