Thermal expansion anomalies and spontaneous magnetostriction in RFe₁₁ Ti single crystals

Abstract

The thermal expansion of single crystals of the tetragonal rare-earth intermetallics RFe₁₁ Ti (R =Y, Gd, Tb, Dy or Ho) has been studied by X-ray dilatometry in the range 5-800 K. The spontaneous volume magnetostriction ω_s, at 5K amounts to about 1 × 10⁻², almost independent of the rare-earth component. At elevated temperatures, ω_s, scales well with the square of the Fe magnetic moment, reflecting the dominant contribution of the Fe-Fe exchange interaction in the magnetostriction phenomena in these intermetallics. The magnetostriction is anisotropic; the basal-plane strain λ _a , far exceeds the uniaxial strain λ _c . In compounds with R =Dy or Tb, a transition from a multiaxial to a uniaxial anisotropy with increasing temperature is accompanied by an additional volume effect of about 1 × 10⁻³. Magnetostrictive distortion (up to 1 × 10⁻³ at 5 K) was observed at low temperatures in the basal plane of TbFe₁₁ Ti.