The magnetic phase diagram of the triangular lattice antiferromagnet CuFeO2
has been studied using single-crystal neutron diffraction measurements in
a magnetic field of up to 14.5 T and also by magnetisation measurements up
to 12 T. At low temperature, two well-defined first-order magnetic phase tr
ansitions were found in this range of applied magnetic field: at H-C1 = 7.6
T and H-C2 = 13.2 T, with the later one corresponding to a transition from
a four to five sublattice structure. Cooling the sample in a high magnetic
field resulted in the locking of the magnetic structure into the intermedi
ate temperature incommensurate structure. (C) 2001 Elsevier Science B.V. Al
l rights reserved.