Spontaneous generation of voltage in the magnetocaloric compound Tb5Si2.2Ge1.8 and elemental Gd

The spontaneous generation of voltage (SGV) in single crystalline Tb5Si2.2Ge1.8 and Gd has been studied. Temperature-induced SGVs were observed along the three principal crystallographic axes of Tb5Si2.2Ge1.8, but not in Gd. Field-induced SGVs were observed with magnetic fields less than 40 kOe applied along the a-axis of Tb5Si2.2Ge1.8, and the c-axis of Gd. The absence of the temperature-induced SGV in Gd indicates the key role first-order phase transformations play in the appearance of the effect when temperature varies. The anisotropy of the magnetic field-induced SGV in Tb5Si2.2Ge1.8 and the existence of the field-induced SGV in Gd, highlight the importance of the magnetocaloric effect in bringing about the SGV.