An inelastic neutron scattering determination of the temperature dependence of the 3d-4f exchange interaction in Sm2Fe17

High energy transfer inelastic neutron scattering has been used to investigate the temperature dependence in the range from 20 to 450 K of the intermultiplet transition E-inter in the intermetallic compound Sm2Fe17. The peak due to this transition, observed in the inelastic neutron spectrum, shifts to lower energies with increasing temperature. From the temperature dependence of E-inter, the temperature dependence of the exchange field B-ex acting on the Sm ion has been established experimentally, as the energy of the intermultiplet transition provides a direct value for the exchange field. At the highest measured temperature T=450 K, which is above the Curie point of 389 K for this compound, the transition energy is situated just above the bare spin-orbit splitting for Sm3+. The method utilized in the present investigation offers a rather easy and direct way to determine B-ex in a large range of Sm intermetallics, which form an interesting class of hard magnetic materials. (C) 2002 Elsevier Science B.V. All rights reserved.