Giant Room-Temperature Magnetostrictions in TbFe2and DyFe2

Huge magnetically induced strains (\ensuremath{\sim}0.2%) were observed in cubic Tb${\mathrm{Fe}}_{2}$ at room temperature. An anomalous "positive" temperature dependence for the magnetostriction is found for Dy${\mathrm{Fe}}_{2}$, yielding a peak in the magnetostriction exceeding 600 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}6}$ 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 $R{\mathrm{Fe}}_{2}$ 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.