Two-dimensional antiferromagnonic activation in S = 1 one-dimensional chain NiTe2O5

Since Haldane conjectured that ground state of one-dimensional Heisenberg antiferromagnet has a finite spin excitation gap for integer spins or gapless excitations for half-odd integer spins, it has inspired lots of theoretical and experimental studies on the low-dimensional quantum magnets. The integer spin chain, called Haldane chain, generally has antiferromagnetic coupling for the intrachain exchange interaction. Recently, we have discovered a new Haldane chain compound NiTe2O5, in which antiferromagnetic order is accompanied by ferromagnetic intrachain coupling and antiferromagnetic interchain coupling. In this research, comprehensive magnetic and thermal properties have been studied in single crystalline as well as polycrystalline NiTe2O5. Interestingly, it has been found that it has two-dimensional antiferromagnonic activation. In this presentation, we explain our intensive experimental studies on NiTe2O5 and discuss about the possible two-dimensional antiferromagnon excitation