title: (31)P NMR study of Na(2)CuP(2)O(7): an S = 1/2 two dimensional Heisenberg antiferromagnetic system.
abstract: The magnetic properties of Na(2)CuP(2)O(7) were investigated by means of (31)P nuclear magnetic resonance (NMR), magnetic susceptibility, and heat capacity measurements. We report the (31)P NMR shift, the spin-lattice [Formula: see text], 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 [Formula: see text] K and a hyperfine coupling A = 3533 ± 185 Oe /μ(B). The (31)P NMR spectrum was found to broaden abruptly below T∼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.
authors.affiliation: Department of Physics, Indian Institute of Technology, Mumbai 400076, India.
authors.forename: R
authors.initials: R
authors.lastname: Nath
authors.forename: A V
authors.initials: AV
authors.lastname: Mahajan
authors.forename: N
authors.initials: N
authors.lastname: Büttgen
authors.forename: C
authors.initials: C
authors.lastname: Kegler
authors.forename: J
authors.initials: J
authors.lastname: Hemberger
authors.forename: A
authors.initials: A
authors.lastname: Loidl