Field-induced Bose-Einstein condensation in zigzag spin chain KGaCu(PO).

Single crystals of GaKCu(PO)were synthesized using the hydrothermal method, and subsequent measurements of specific heat, magnetic susceptibility, and high-field magnetization were performed. A broad peak is observed in the magnetic susceptibility and specific heat curves, with the maximum values appearing at about 11.5 K and 5.29 K, respectively. The highest maximum peak value of susceptibility is observed when the magnetic field is applied along the-axis, followed by the-axis,axis, and polycrystalline samples. These indicate that the system exhibits one-dimensional magnetism and the magnetic easy axis is theaxis. The magnetization at 2 K reveals the occurrence of a field-induced Bose-Einstein condensation (BEC) phase within the magnetic field range of approximately 8-12 T. High-field magnetization up to 40 T indicates that the compound reaches magnetization saturation as the field exceeds= 12 T. Through systematic measurements, a field-temperature (-) phase diagram was constructed, and dome-like phase boundaries were observed. The findings suggest that GaKCu(PO)is a spin gap system and a promising candidate for studying BEC of magnons due to its phase transition boundary occurring at low magnetic fields.