Effects of Al and Fe solubility on the magnetofunctional properties of AlFe2B2

Bridgman single-crystal growth of ${\mathrm{AlFe}}_{2}{\mathrm{B}}_{2}$ resulted in systematic Fe-Al lattice site substitution in the ${\mathrm{AlFe}}_{2}{\mathrm{B}}_{2}$ (${\mathrm{Mn}}_{2}{\mathrm{AlB}}_{2}$-type structure, aka $1\text{\ensuremath{-}}2\text{\ensuremath{-}}2$) phase along the direction of solidification. The Fe:Al ratio varied from 1.94 to 2.06. The $1\text{\ensuremath{-}}2\text{\ensuremath{-}}2$ phase lattice parameters, magnetic transition temperatures (${T}_{t}$) $280\ensuremath{-}315$ K, magnetic entropy changes $(\mathrm{\ensuremath{\Delta}}S)2.3\ensuremath{-}4.0\phantom{\rule{0.16em}{0ex}}\mathrm{J}/\mathrm{kg}\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, heat capacity (${C}_{p}$) $117\ensuremath{-}147\phantom{\rule{0.16em}{0ex}}\mathrm{J}/\mathrm{mol}\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and thermal conductivity $(\ensuremath{\kappa})\ensuremath{\sim}2.4\ensuremath{-}11.5\phantom{\rule{0.16em}{0ex}}\mathrm{W}/\mathrm{m}\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ all varied monotonically across the region of solubility. These findings confirm the sensitivity of the magnetic and thermal properties of the ${\mathrm{AlFe}}_{2}{\mathrm{B}}_{2}$ compound to antisite defects. The interplay between Al and Fe lattice site occupancy and the resultant magnetic and electronic responses facilitates tailoring the properties of the ${\mathrm{AlFe}}_{2}{\mathrm{B}}_{2}$ system for potential functional applications, including magnetic cooling.