Magnetostriction of AlFe2B2 in High Magnetic Fields

TL;DR

This study investigates the anisotropic magnetostriction of polycrystalline AlFe2B2 near its Curie temperature using high magnetic fields, combining experimental measurements with theoretical calculations to understand lattice changes under magnetic influence.

Contribution

It provides the first detailed experimental analysis of AlFe2B2's magnetostriction in high magnetic fields near TC, supported by density functional theory and Landau model estimations.

Findings

Lattice parameters change anisotropically near TC

c-axis expands while a- and b-axes contract with field

Magnetostriction volume change sign across TC

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.