Abstract
We present the synthesis and a detailed investigation of structural and magnetic properties of polycrystalline by means of x-ray diffraction, magnetic susceptibility, electron spin resonance, and nuclear magnetic resonance measurements. Temperature-dependent magnetic susceptibility could be described well using a weakly coupled spin- dimer model with an excitation gap K between the singlet ground state and triplet excited states and a weak interdimer exchange coupling K. A gapped chain model also describes the data well with a gap of about 20 K. The electron spin resonance intensity as a function of temperature traces the bulk susceptibility nicely. The isotropic Landé factor is estimated to be about , at room temperature. We are able to resolve the NMR signal as coming from two inequivalent P sites in the crystal structure. The hyperfine coupling constant between nucleus and spins is calculated to be Oe/ and Oe/ for the P(1) and P(2) sites, respectively. Our NMR shift and spin-lattice relaxation rate for both the sites show an activated behavior at low temperatures, further confirming the singlet ground state. The estimated value of the spin gap from the NMR data measured in an applied field of T is consistent with the gap obtained from the magnetic susceptibility analysis using the dimer model. Because of a relatively small spin gap, is a promising compound for further experimental studies under high magnetic fields.
- Received 11 November 2016
- Revised 1 February 2017
DOI:https://doi.org/10.1103/PhysRevB.95.174421
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