X-ray diffraction studies on magneto-volume effect and the first order phase transition in Lu(Co1-xGax)2

The magneto-volume effect in Laves phase compound Lu(Co1-chiGachi)(2) has been studied by an X-ray diffraction technique. The temperature dependence of the volume change for the samples with 0.10 less than or equal to chi less than or equal to 0.15 has been found to be proportional to the square of magnetization with the same coefficient of the magneto-volume coupling constant. For the sample with chi = 0.10, the temperature induced first order transition from the cubic to the tetragonal structure has been observed. Above the Curie temperature, a discontinuous change of the lattice parameter is also observed by applying magnetic field. The results can be described by a spin fluctuation theory for itinerant electron metamagnets. The temperature and magnetic field induced first order phase transitions observed in the sample with chi = 0.10 are characterized by the coexistence of two phases in a wide temperature or magnetic field range without an appreciable hysteresis.