MAGNETIZATION CURVES OF ANTIFERROMAGNETIC HEISENBERG SPIN-1 2 LADDERS/

Magnetization processes of spin-1/2 Heisenberg ladders are studied usi ng strong-coupling expansions, numerical diagonalization af finite sys tems, and a bosonization approach. We find that the magnetization exhi bits plateaux as a function of the applied field at certain rational f ractions of the saturation value. Our main focus is on ladders with th ree legs where plateaux with magnetization one third of the saturation value are shown to exist.