Magnetovolume and magnetocaloric effects in Er2Fe17.

Combining different experimental techniques, investigations in hexagonal P63/mmc Er2Fe17 show remarkable magnetovolume anomalies below the Curie temperature, Tc. The spontaneous magnetostriction reaches 1.6 x 10-2 at 5 K and falls to zero well above Tc, owing to short-range magnetic correlations. Moreover, Er2Fe17 exhibits direct and inverse magnetocaloric effects (MCE) with moderate isothermal magnetic entropy △SM, and adiabatic temperature △Tad changes [△SM ~ --4.7 J(kgK)-1 and △Tad ~ 2.5 K near the Tc, and △SM ~ 1.3 J(kgK)-1 and △Tad[1 ~ --0.6 K at 40 K for △H = 80 kOe, respectively, determined from magnetization measurements]. The existence of an inverse MCE seems to be related to a crystalline electric field-level crossover in the Er sublattice and the ferrimagnetic arrangement between the magnetic moments of the Er and Fe sublattice. The main trends found experimentally for the temperature dependence of △SM and △Tad as well as for the atomic magnetic moments are qualitatively well described considering a mean-field Hamiltonian that incorporates both crystalline electric field and exchange interactions. △SM(T) and △Tad(T) curves are essentially zero at ~150 K, the temperature where the transition from direct to inverse MCE occurs. A possible interplay between the MCE and the magnetovolume anomalies is also discussed. [ABSTRACT FROM AUTHOR]