Possible field-induced quantum state in a rhombic lattice antiferromagnet KCoPOHO

Fujihara, Masayoshi ; Hagihara, Masato   ; Koda, Akihiro*; Nakamura, Jumpei*; Matsuo, Akira*; Kindo, Koichi*; Ishikado, Motoyuki*

We reported the magnetic behavior of a rhombic lattice quantum antiferromagnet KCoPOHO. The rhombic lattice model is equivalent to a model of a square lattice with two different diagonal components, and competing exchange interactions potentially produce exotic quantum states. This compound is well characterized by the = 1/2 state. The magnetic structure of KCoPOHO is identified as an incommensurate helical structure, characterized by a magnetic modulation propagation vector = (0.1747(1) 0 0) with an in-plane moment rotating along the axis. Moreover, a magnetic field-induced phase transition is observed at approximately 1 T. The application of a magnetic field suppresses spin ordering and enhance spin fluctuations. Our experimental results suggest the presence of a quantum phase in the magnetic phase diagram of the spin-1/2 Heisenberg rhombic lattice antiferromagnet with easy-plane anisotropy.