1/3 magnetization plateau observed in the spin-1/2 trimer chain compound Cu3(P2O6OH)2

We report magnetic properties of Cu-3(P2O6OH)(2). A spin-1/2 trimer chain with J(1)-J(2)-J(2) interactions exists, where J(1) and J(2) denote two antiferromagnetic (AF) exchange interactions. A 1/3 magnetization plateau was observed above 12 T in a magnetization curve at 1.6 K. The appearance of the plateau is consistent with the theorem of Oshikawa, Yamanaka, and Affleck [Phys. Rev. Lett. 78, 1984 (1997)]. Experimental results of magnetic susceptibility and magnetization agree well with quantum Monte Carlo results for the trimer chain with J(1)=95 and J(2)=28 K. To our knowledge, Cu-3(P2O6OH)(2) is the first model compound of trimer chains with only AF interactions showing a magnetization plateau.