Study of one-dimensional nature of (Sr,Ba)_2Cu(PO_4)_2 and BaCuP_2O_7 via 31P NMR

TL;DR

This study investigates the one-dimensional magnetic properties of (Sr,Ba)_2Cu(PO_4)_2 and BaCuP_2O_7 using 31P NMR, revealing their behavior aligns with the S=1/2 Heisenberg antiferromagnetic chain model and identifying magnetic ordering in BaCuP_2O_7.

Contribution

The paper provides detailed NMR measurements confirming the 1D magnetic nature of these phosphates and determines their exchange interactions, with new insights into magnetic ordering in BaCuP_2O_7.

Findings

NMR shift K(T) fits the S=1/2 Heisenberg chain model

Exchange interactions J/k_B are 165 K, 151 K, and 108 K for the compounds

Magnetic ordering occurs at 0.8 K in BaCuP_2O_7

Abstract

The magnetic behavior of the low-dimensional phosphates (Sr,Ba)_2 Cu(PO_4)_2 and BaCuP_2O_7 was investigated by means of magnetic susceptibility and ^{31}P nuclear magnetic resonance (NMR) measurements. We present here the NMR shift K(T), the spin-lattice 1/T_1 and spin-spin 1/T_2 relaxation-rate data over a wide temperature range 0.02 K < T < 300 K. The T-dependence of the NMR K(T) is well described by the S=1/2 Heisenberg antiferromagnetic chain model with an intrachain exchange of J/k_B = 165 K, 151 K, and 108 K in Sr_2Cu(PO_4)_2, Ba_2Cu(PO_4)_2, and BaCuP_2O_7, respectively. Our measurements suggest the presence of magnetic ordering at 0.8 K in BaCuP_2O_7 (J/k_B = 108 K). For all the samples, we find that 1/T_1 is nearly T-independent at low-temperatures (1 K < T < 10 K), which is theoretically expected for 1D chains when relaxation is dominated by fluctuations of the staggered susceptibility. At high temperatures, 1/T_1 varies nearly linearly with temperature.