High-field magnetostriction and magnetization of DyFe2 and TbFe2

Using pulsed magnetic fields up to 18 T, measurements have been carried out of the magnetostriction and magnetization of polycrystalline DyFe2 and TbFe2 over the temperature range 4.2-300 K. In the case of TbFe2 the magnetostriction isotherms at all temperatures show a tendency to saturate at high field levels. The total magnetostriction decreases monotonically and is roughly proportional to the cube of the reduced magnetization. An extrapolation to infinite field and zero temperature gives a value for the saturation magnetostriction of TbFe2 of lambda sub(s) = 3.34 x 10-3. Assuming the polycrystalline sample to be an aggregate of non-interacting, single-domain particles it is estimated that the single-crystal magnetostriction constants are lambda111 = 4.53 x 10-3 and lambda100 5.2 x 10-3 at 16 K. For DyFe2 the magnetostriction isotherms below 100 k are linear in magnetic field with zero remanence. In contrast to this behaviour, the magnetization in the same temperature range shows the rapid rise at low fields which is characteristic of domain-wall movement. Estimates are made of the magnetostrictive contribution to domain energy in the case when 900 domain walls are present. The possibility that the discrepancy between magnetostriction and magnetization data can be explained in terms of a lack of 900 domain walls is discussed, along with the alternative conclusion that lambda100<= lambda111 at low temperatures. (author)