High-field magnetization measurements have been performed on single crystals of ambient pressure (AP) and high-pressure (HP) phases of (VO)2P2O7 (VOPO). In the measurement of AP-VOPO, we observed magnetization rises with the curvatures changing at two critical fields. On the other hand, a single sharp increase was observed in the magnetization curve of HP-VOPO. These behaviors revealed that AP-VOPO and HP-VOPO consist of two kinds of gapped chains and a single gapped chain, respectively. From convex behaviors in these magnetization m, we estimated the critical exponent δ = 4/3 defined as m ∝(H-Hc)1/δ for the S = 1/2 gapped system.
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