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DOE OSTI · 1817628

Borderline first-order magnetic phase transition in AlFe 2 B 2

Lejeune, B. T.·Barua, R.·Mudryk, Y.·Kramer, M. J.·McCallum, R. W.·Pecharsky, V.·Lewis, L. H.
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Abstract

The thermal evolution of lattice parameters coupled with heat capacity data provide insight into tailorable magnetism-structure attributes in the orthorhombic compound AlFe 2 B 2 that was synthesized with and without small additions of gallium. Temperature-dependent X-ray powder diffraction experiments conducted through the magnetic phase transition reveal that the a- and b-parameters of both samples increase with increasing temperature while the c-parameter decreases. While a weak volumetric thermal expansion is noted over a range of temperatures well below and above the magnetic phase transition, anomalous behavior was observed within the phase transition region itself to reveal a magnetostructural phase transition with borderline first-order character in the Ga-modified sample but of more second-order character in the Ga-free sample. It is established that the nearest-neighbor Fe-Fe interatomic distance within the (ab)-plane plays a dominant role in influencing the magneto-functional response of these compounds. The magnetocaloric properties are discussed in the context of temperature-induced changes of the interatomic bonding that are influenced by the hypothesized presence of iron antisite defects in the AlFe 2 B 2 lattice.

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Lejeune, B. T., Barua, R., Mudryk, Y., Kramer, M. J., McCallum, R. W., Pecharsky, V., Lewis, L. H.. 2021-07-13. Borderline first-order magnetic phase transition in AlFe 2 B 2. https://doi.org/10.1016/j.jallcom.2021.161150

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