  The structural and magnetic properties of Y1-xErxFe2 intermetallic compounds
and their hydrides and deuterides Y1-xErxFe2H(D)4.2 have been investigated
using X-ray diffraction and magnetic measurements under static and pulsed
magnetic field up to 60 T. The intermetallics crystallize in the C15 cubic
structure , whereas corresponding hydrides and deuterides crystallize in a
monoclinic structure. All compounds display a linear decrease of the unit cell
volume versus Er concentration; the hydrides have a 0.8% larger cell volume
compared to the deuterides with same Er content. They are ferrimagnetic at low
field and temperature with a compensation point at x = 0.33 for the
intermetallics and x = 0.57 for the hydrides and deuterides. A sharp first
order ferromagnetic-antiferromagnetic (FM-AFM) transition is observed upon
heating at TFM-AFM for both hydrides and deuterides. These compounds show two
different types of field induced transitions, which have different physical
origin. At low temperature (T < 50 K), a forced ferri-ferromagnetic
metamagnetic transition with Btrans1 = 8 T, related to the change of the Er
moments orientation from antiparallel to parallel Fe moment, is observed.
Btrans1 is not sensitive to Er concentration, temperature and isotope effect. A
second metamagnetic transition resulting from antiferromagnetic to
ferrimagnetic state is also observed. The transition field Btrans2 increases
linearly versus temperature and relates to the itinerant electron metamagnetic
behavior of the Fe sublattice. An onset temperature TM0 is obtained by
extrapolating TFM-AFM (B) at zero field. TM0 decreases linearly versus the Er
content and is 45(5) K higher for the hydrides compared to the corresponding
deuteride. The evolution of TM0 versus cell volume shows that it cannot be
attributed exclusively to a pure volume effect and that electronic effects
should also be considered.
