Influence of Si and Co substitutions on magnetoelastic properties of R2Fe17 (R=Y, Er and Tm) intermetallic compounds

Abstract The magnetostriction of the off-stoichiometric R 2 Fe 17 -type intermetallic compounds based on R 2 Fe 14− x Co x Si 2 (R=Y, Er, Tm and x =0, 4) was measured, using the strain gauge method in the temperature range 77–460 K under applied magnetic fields up to 1.5 T. All compounds show sign change and reduction in magnetostriction values compared to the R 2 Fe 17 compounds by Si substitution. For Y 2 Fe 14 Si 2 and Er 2 Fe 14 Si 2 , saturation behaviour is observed near magnetic ordering temperature ( T C ), whereas for Tm 2 Fe 14 Si 2 , saturation starts from T >143 K. Also, Co substitution has different effects on the magnetostriction of R 2 Fe 14 Si 2 compounds. In Er 2 Fe 10 Co 4 Si 2 and Tm 2 Fe 10 Co 4 Si 2 , saturation occurs below the spin reorientation temperature ( T SR ). In addition, in Er 2 Fe 14 Si 2 , a sign change occurs in the anisotropic magnetostriction (Δ λ ) as well as the volume magnetostriction (Δ V / V ) at their T SR values. The volume magnetostrictions of the Tm-containing compounds show an anomaly around their T SR . In R 2 Fe 14 Si 2 compounds, parastrictive behaviour is also observed in Δ V / V near their T C values. In addition, the magnetostriction of the sublattices is investigated. Results show that in R 2 Fe 14 Si 2 compounds, the rare-earth sublattice contribution to magnetostriction is negative and comparable to the iron sublattice, whereas, in R 2 Fe 10 Co 4 Si 2 compounds, the rare-earth sublattice contribution is positive and larger than Fe sublattice. These results are discussed based on the effect of Si and Co substitutions on the anisotropy field of these compounds. Influence of the spin reorientation transition on the magnetostriction of these compounds is discussed in terms of the anisotropic sublattice interactions.