Magnetization process and the associated lattice deformations in an intermetallic compound Gd₅Ge₃

The results of magnetization and synchrotron X-ray diffraction measurements on Gd₅Ge₃ subject to a pulsed high magnetic field are reported. When the magnetic field, H, is applied parallel to the a-axis, a sudden increase in magnetization, M, has been observed at ∼3.8 T. For H ∥ c, M increases monotonically with H. The magnetization becomes saturated above about 30 T for the two orientations. The lattice constant, a elongates, while c shrinks with increasing H. We calculate the exchange energy under applied magnetic fields based on the proposed magnetic structure assuming an antiferromagnetic exchange interaction in the a-a plane and a ferromagnetic one along the c-axis. We are successful in explaining the opposing behavior of the lattice deformations. Our calculation shows that the change in the lattice constants is proportional to M², in agreement with the observation.