Field-induced spin liquids and orders in quasi-1D gapped systems

The field-induced long-range antiferromagnetic order in the quasi-1D bond-alternating spin system is investigated with the mean field approximation for interchain interaction. The obtained phase diagram in the H-T plane indicated no enhancement of the Neel temperature around the critical fields, although the critical exponent η characterizing the Tomonaga-Luttinger liquid behavior indicates the antiferromagnetic spin correlation is stronger than at intermediate fields. The experimental phase diagram of F5PNN is well reproduced