Gadolinium diiodide is an inorganic compound, with the chemical formula of GdI<sub>2</sub>. It is an electride, with the ionic formula of Gd<sup>3+</sup>(I<sup>âÂÂ</sup>)<sub>2</sub>e<sup>âÂÂ</sup>, and therefore not a true gadolinium(II) compound. It is ferromagnetic at 276 K with a saturation magnetization of 7.3 B; it exhibits a large negative magnetoresistance (~70%) at 7 T near room temperature. It can be obtained by reacting gadolinium and gadolinium(III) iodide at a high temperature:
It can react with hydrogen at high temperature (800 ðC) to obtain gadolinium hydrogen iodide (GdI<sub>2</sub>H<sub>0.97</sub>).