Magnetostriction in AlFe₂B₂ in 25 T DC field near room temperature

Using the experimental capability of the novel X-ray diffraction instrument available at the 25 Tesla Florida Split Coil Magnet at the NHMFL, Tallahassee an extensive investigation on the magnetostriction of polycrystalline AlFe₂B₂ have been performed. The DC magnetization measurements confirm the ferromagnetic transition temperature T_C to be 283 K. The magnetostriction was measured near T_C, at 250, 290, and 300 K. AlFe₂B₂ exhibits an anisotropic change in lattice parameters as a function of magnetic field near the T_C, and a monotonic variation as a function of applied field has been observed. The c-axis increases significantly while the a- and b-axes decrease with the increasing field in the vicinity of T_C, irrespective of the measurement temperature. The volume magnetostriction decreases with decreasing temperature and changes its sign across T_C. Density functional theory calculations for the non-polarized and spin-polarized (ferromagnetic) models confirm that the observed changes in lattice parameters due to spin polarization are consistent with the experiment. The relationships for magnetostriction are estimated based on a simplified Landau model that agrees well with the experimental results.