Influence of Si and Co substitutions on magnetoelastic properties of R 2Fe 17 (R=Y, Er and Tm) intermetallic compounds

Abstract

The magnetostriction of the off-stoichiometric R 2Fe 17-type intermetallic compounds based on R 2Fe 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 2Fe 17 compounds by Si substitution. For Y 2Fe 14Si 2 and Er 2Fe 14Si 2, saturation behaviour is observed near magnetic ordering temperature ( T C), whereas for Tm 2Fe 14Si 2, saturation starts from T>143 K. Also, Co substitution has different effects on the magnetostriction of R 2Fe 14Si 2 compounds. In Er 2Fe 10Co 4Si 2 and Tm 2Fe 10Co 4Si 2, saturation occurs below the spin reorientation temperature ( T SR). In addition, in Er 2Fe 14Si 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 2Fe 14Si 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 2Fe 14Si 2 compounds, the rare-earth sublattice contribution to magnetostriction is negative and comparable to the iron sublattice, whereas, in R 2Fe 10Co 4Si 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.