Anisotropic magnetostriction of CeAl2near its antifeeromagnetic transition

Abstract

The magnetostriction of polycrystalline samples of Ce${\mathrm{Al}}_2$ has been measured as a function of temperature and magnetic field in the vicinity of its low-temperature phase transition. We find that the magnetostrictive response is dominantly anisotropic, reflecting the anisotropy of the $4f$ charge distribution. The volume magnetostriction upon entering the low-temperature phase (LTP) precludes any significant valence change of the Ce atoms. The anisotropic magnetostriction in the LTP indicates the development of a spontaneous antiferromagnetic (AF) ordering transverse to the external field. Studies of the orientation of this transverse AF polarization show both irreproducible domain orientation in field and a reversible orientation due apparently to a continuous microscopic rotation of the AF order parameter.