Analysis of the temperature-field dependence of the magnetostriction in the antiferromagnetic phase of the easy-plane antiferromagnet CoCl2

An analysis is made of the experimental magnetic-field curves of the anisotropic (in the easy-plane) magnetostriction of the antiferromagnet CoCl2 at different temperatures in the ordered phase. It is shown that the field dependence of the magnetostriction in a single-domain antiferromagnetic state remains proportional to the square of the applied field over the entire temperature range; this behavior corresponds well to the classic (Neel) scheme of collapse of the sublattice spins (spin flip). The temperature dependences of the intrasublattice and intersublattice contributions to the magnetoelasticity are proportional to each other. The temperature dependence of the spin-flip field obtained from the magnetostriction data agrees with that obtained previously from observations of the antiferromagnetic resonance (AFMR). The temperature dependence of the spontaneous anisotropy of the magnetostriction, obtained by extrapolating the magnetostriction in the single-domain state to zero field, is close to M similar to T-4. (C) 2000 American Institute of Physics. [S1063-777X(00)00707-6].