Metamagnetism of itinerant d-electrons in Laves phase compounds Lu(Co_1-xAl_x)₂

Abstract

Representative first-order metamagnetic transitions with a large hysteresis have been observed for x<or=0.06. The transition field Hc for x=0.06 is 220 kOe at 4.2 K. Simple but strong ferromagnetism is found for x>0.12. A mixing state of ferromagnetic and paramagnetic states of Co is assumed for 0.06<or=x<or=0.12. The paramagnetic component in the state also exhibits the metamagnetic transition. By surveying the temperature dependence of metamagnetism, a boundary temperature of the first- and second-order metamagnetic transitions, and a first-order magnetic transition in thermomagnetic curves are found for the first time. In relation to the magnetic phase transitions the critical parameters T1 and H1 are introduced and discussed. Finally a magnetic phase diagram is presented.