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(Co 1- x Ga x ) 2 has been studied by an X-ray diffraction technique. The temperature dependence of the volume change for the samples with 0.10≤ x ≤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 x =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 x =0.10 are characterized by the coexistence of two phases in a wide temperature or magnetic field range without an appreciable hysteresis.