Crystallography, anisotropic metamagnetism, and magnetocaloric effect in Tb5Si2.2Ge1.8

The metamagnetic-like transitions and giant magnetocaloric effect were observed with the magnetic field applied parallel to the $a$ and $c$ axes, but not the $b$ axis in a ${\mathrm{Tb}}_{5}{\mathrm{Si}}_{2.2}{\mathrm{Ge}}_{1.8}$ single crystal. The in situ x-ray powder diffraction study indicates that these metamagnetic-like transitions are coupled to crystallographic phase transformations occurring via strong magnetoelastic interactions. The magnetocrystalline anisotropy plays an important role in this system. Magnetic fields less than $40\phantom{\rule{0.3em}{0ex}}\mathrm{kOe}$ cannot drive either the magnetic or the crystallographic phase transition to completion for ${\mathrm{Tb}}_{5}{\mathrm{Si}}_{2.2}{\mathrm{Ge}}_{1.8}$ powder due to the strong single ion anisotropy of Tb.