Specific heat measurements in a magnetic field up to 8 T have been performed on an S = 1/2 weakly coupled alternating ferromagnetic (F) and antiferromagnetic (AF) dimer chain system, (CH3)2NH 2-CuCl3. We have observed a spontaneous AF ordering and a field-induced one below and above the 1/2 magnetization plateau field range from 2 to 3.5 T, respectively. The H-T phase boundaries for the orderings are completely different from the general reentrant ones of the other quantum spin systems investigated thus far. In the plateau field range, a double-peaked structure is observed in the temperature dependence of specific heat, reflecting the coexistence of F and AF excitations.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)