## Abstract

The magnetic properties of Na2CuP2O7 were investigated by means of P-31 nuclear magnetic resonance (NMR), magnetic susceptibility, and heat capacity measurements. We report the 31P NMR shift, the spin-lattice (1/T-1), and spin spin (1/T-2) relaxation rate data as a function of temperature T. The temperature dependence of the NMR shift K(T) is well described by the S = 1/2 square lattice Heisenberg antiferromagnetic model with an intraplanar exchange of J/k(B) similar or equal to 18 +/- 2 K and a hyperfine coupling A = 3533 +/- 185 Oe/mu B. The P-31 NMR spectrum was found to broaden abruptly below T similar to 10 K, signifying some kind of transition. However, no anomaly was noticed in the bulk susceptibility data down to 1.8 K. The heat capacity appears to have a weak maximum around 10 K. With decrease in temperature, the spin-lattice relaxation rate 1/T-1 decreases monotonically and appears to agree well with the high temperature series expansion expression for a S = 1/2 2D square lattice.

Original language | English |
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Pages (from-to) | 4285-4294 |

Number of pages | 10 |

Journal | Journal of Physics: Condensed Matter |

Volume | 18 |

DOIs | |

Publication status | Published - 2006 |

## Keywords

- NUCLEAR MAGNETIC-RELAXATION
- QUANTUM ANTIFERROMAGNETS
- GROUND-STATES
- SUSCEPTIBILITY
- LA2CUO4
- KCUF3