Magnetostriction of AlFe2B2 in high magnetic fields

Abstract

Using the experimental capability of the novel X-ray diffraction instrument available at the 25 Tesla Florida Split Coil Magnet at the NHMFL, Tallahassee we present an extensive investigation on the magnetostriction of polycrystalline AlFe2B2. The magnetostriction was measured near the ferromagnetic transition temperature (Curie temperature TC = 280 K, determined via DC magnetization measurements), namely, at 250, 290, and 300 K. AlFe2B2 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 the increasing field in the vicinity of TC, irrespective of the measurement temperature. The volume magnetostriction decreases with decreasing temperature and changes its sign across TC. 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.

Exploring Doping Effects on Magnetocaloric, Magnetoelastic, and Magnetostriction Properties of Fe2AlB2: A First-Principles Study

“…The most significant expansion occurs in the z direction when the magnetic saturation is aligned with the x direction, corresponding to λ 5 . In Fe 2 AlB 2 , the magnetostriction exhibits anisotropy, which is consistent with experimental findings . However, it is noteworthy that the sign of the λ values obtained from our calculations differs from those observed in experiments at 250, 290, and 300 K .…”

“…In Fe 2 AlB 2 , the magnetostriction exhibits anisotropy, which is consistent with experimental findings . However, it is noteworthy that the sign of the λ values obtained from our calculations differs from those observed in experiments at 250, 290, and 300 K . It is important to consider that the magnetoelastic effect is highly sensitive to temperature.…”

“…Here, a fm and a nm are the optimized lattice parameters at T = 0 K for the spin polarized and unpolarized calculations, respectively. For pristine Fe 2 AlB 2 , Δ a , Δ b , and Δ c are 5.28, −0.98, and −2.49%, respectively, in line with experiments. , We should note that the changes in the experimental lattice parameters upon magnetic ordering are significantly smaller. Our results indicate that the Fe 2 AlB 2 crystal exhibits contraction along the a direction, while it undergoes extension along the b and c directions at the magnetic to nonmagnetic transition.…”