A special limit of an antiferromagnetic XYZ chain was recently shown to exh
ibit interesting bulk as well as surface spin-flop transitions at T = 0. He
re we provide a complete calculation of the thermodynamics of the bulk tran
sition using a transfer-matrix renormalization-group method that addresses
directly the thermodynamic limit of quantum spin chains. We also shed some
light on certain spin-wave anomalies at low temperature predicted earlier b
y Johnson and Bonner.