Spin-1/2 chain compound Ba_2Cu_2Te_2P_2O_(13): Magnetization, specific heat, and local-probe NMR

摘要

We present synthesis and characterization of Ba_2Cu_2Te_2P_2O_(13) (BCTPO) via x-ray diffraction, magnetic susceptibility, heat capacity, and ~(31)P nuclear magnetic resonance (NMR) measurements. BCTPO crystallizes in a monoclinic structure with Cu~(2+) ions forming coupled chains. In magnetization M(T) measurements, a broad maximum is observed around 53 K. Upon the application of magnetic fields, a sharp anomaly evolves around 4 K in the heat capacity C_P(T) data, indicative of long-range order, while it is absent in zero field. The ~(31)P NMR line shift at about 93.954 kOe tracks the spin susceptibility, whereas the line broadening evidences the onset of magnetic order at about 4 K or lower. The inferred isotropic and axial components of the hyperfine coupling constant are A_(hf)~(iso) ≃ 3635 Oe/μ_B and A_(hf)~(ax) ≃ 479 Oe/μ_B, respectively. The ~(31)P NMR spin-lattice relaxation rate 1/T_1 shows a pronounced divergence for T → 0. We assign this behavior to critical fluctuations on the verge of order.