Magnetic susceptibility and resistivity of R(CO,A)2 where R=Y, Sc and A=Al, Si

Weak itinerant ferromagnetism appears in the Laves-phase compounds RCo2 (R=Y, Lu, Sc) as Al is substituted for Co, with a simultaneous increase in lattice constant. The Lu system has the maximum Tc (145 K) and a Co moment (0.65μB approximately 6 times those of the Y and Sc systems. This is unexpected since it is intermediate in lattice constant among these three systems. To investigate this the alloys (Y0.7Sc0.3)(Co,Al)2 were formed, which are comparable in lattice constant to Lu(Co,Al)2. In addition the alloys Y(Co,Si)2 and Sc (Co,Si)2 were made where substitution of Si for Co depletes the Co 3d band just as with Al substitution, but with about one-tenth the change in lattice constant. Magnetic-susceptibility and electrical-resistivity data for T=2–300 K are presented and discussed.