FIELD-INDUCED TWO-MAGNON NUCLEAR SPIN-LATTICE RELAXATION IN ORDERED QUADRATIC-LAYER ANTIFERROMAGNETS A. J. Van Der Wal et H.W. De Wijn J. Phys. Colloques, 39 C6 (1978) C6-757-C6-758 DOI: 10.1051/jphyscol:19786338