Magnetovolume and magnetocaloric effects in Er2Fe17

Abstract

"Combining different experimental techniques, investigations in hexagonal P6(3)/mmc Er2Fe17 showremarkable magnetovolume anomalies below the Curie temperature, T-C. The spontaneous magnetostriction reaches 1.6 x 10(-2) at 5Kand falls to zero well above T-C, owing to short-range magnetic correlations. Moreover, Er2Fe17 exhibits direct and inverse magnetocaloric effects (MCE) with moderate isothermal magnetic entropy Delta S-M, and adiabatic temperature Delta T-ad changes [Delta S-M similar to -4.7 J(kgK)(-1) and Delta T-ad similar to 2.5 K near the T-C, and Delta S-M similar to 1.3 J(kgK)(-1) and Delta T-ad similar to -0.6 K at 40 K for Delta 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 Delta S-M and Delta T-ad 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. Delta S-M (T) and Delta T-ad(T) curves are essentially zero at similar to 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."