Magnetostriction of AlFe2B2 in high magnetic fields

Abstract

Using the experimental capability of the x-ray diffraction instrument available at the 25-T Florida split coil magnet at the NHMFL, we investigated the magnetostriction of polycrystalline $\mathrm{Al}{\mathrm{Fe}}_{2}{\mathrm{B}}_{2}$. The magnetostriction was measured in the vicinity of the ferromagnetic transition with ${T}_{C}=280\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, at 250, 290, and 300 K. $\mathrm{Al}{\mathrm{Fe}}_{2}{\mathrm{B}}_{2}$ exhibits an anisotropic change in lattice parameters as a function of magnetic field near the Curie temperature, and a monotonic variation as a function of applied field has been observed, i.e., the $c$ axis increases significantly while the $a$ and $b$ axes decrease with 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 nonpolarized 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.