Gd<sup>3+</sup> rattling triggered by a “weak” M–I transition at 140–160 K in the Ce<sub>1−<i>x</i></sub>Gd<sub><i>x</i></sub>Fe<sub>4</sub>P<sub>12</sub> (<i>x</i> ≈ 0.001) skutterudite compounds: An ESR study
Physica status solidi. B, Basic research