Chiral and helical phase transitions in quasi-1D molecular magnets

We review recent experimental data obtained with quasi-one-dimensional (1D) molecular magnets Gd(hfac)3NITR. For Gd(hfac)3NITiPr the results can be coherently explained only in terms of the Villain's conjecture: a chiral order at intermediate temperatures and helical order at low temperatures. In the case of weakly frustrated molecular magnetic chain compounds Gd(hfac)3NITPh, new specific heat measurements show the presence of a phase transition to the three-dimensional (3D) helical order, observed at T approx 0.63 K. In the temperature range 25-250 mK the experimental specific heat data are reproduced very well by a simple spin wave theory.