An X-Ray Absorption Study of Stoichiometry and Bonding in the Maagnetocaloric Antiperovskite Mn3GaC
L H. Lewis, D Yoder, A R. Moodenbaugh, Daniel A. Fischer, M-H Yu
The effects of carbon content were studied with magnetic and spectroscopic techniques in the imtermetallic perovskite compounds Mn3GaC, Mn3GaC0.90, and Mn3GaC0.78. Mn3GaC undergoes a first order magnetic transition near 160 K which is associated with a remarkable magnetocaloric effect: these effects are suppressed in the substoichiometric compositions. X-ray absorption spectroscopy (XAS) measurements were conducted to provide insight into the electronic structure of these materials and its effect on the magnetostructural transition. The temperature dependence of the C K-edge for Mn3GaC reveals no observable change with temperature across the first-order magnetic transition. Room temperature C K-edge XAS variations are reported for the three compositions. FEFF 8.2 calculations are in good qualitative agreement with data for the stoichiometric sample, but do not correlate with the changes in XAS observed in C-deficient samples. Based on these results and application of the Goodenough-Anderson-Kanamori rules, a phenomenological model for the C content dependence of the low temperature phase transitions is developed. A deficiency of carbon atoms in the substoichiometric compositions promotes near-neighbor 90 degree Mn-Mn ferromagnetic pairs, which at low temperature control the magnetic state.
Physical Review Letters
Antiperovskite, magnetocaloric, NEXAFS
, Yoder, D.
, Moodenbaugh, A.
, Fischer, D.
and Yu, M.
An X-Ray Absorption Study of Stoichiometry and Bonding in the Maagnetocaloric Antiperovskite Mn<sub>3</sub>GaC, Physical Review Letters
(Accessed June 9, 2023)