Abstract
1H and 195Pt NMR are used to probe the spin ½ anion chain in the quasi-one-dimensional conductor Per2[Pt(mnt)2], which exhibits nearly simultaneous charge density wave (CDW) and spin-Peierls (SP) transitions at low temperatures (Tc ~ 8 K). Below Tc the [Pt(mnt)2] chain forms a spin-singlet state that is evident in 1H NMR spectra and spin relaxation (1/T1) rates; however minority unpaired Pt spins may remain in the SP ground state. With increasing magnetic field, the SP and CDW order parameters decrease in unison, indicating they are coupled up to a critical field Bc ~ 20 T. Above Bc, the spin singlet evolves into a spin-polarized configuration. The 195Pt NMR signals vanish as either Tc or Bc are approached from within the SP ground state, suggesting the hyperfine field of the Pt nucleus is significantly stronger than at the proton sites. Simulations yield a consistent picture of the angular, temperature, and magnetic field-dependent spectral features.
Highlights
Introduction dimensional conductors in the seriesPer2[M(mnt)2] (PerPer = perylene; M = Au, Two-chain quasi-one-dimensionalPt, Pd, Co, etc.) have long been studied due to the unique nature of their the parallel, parallel interacting chain structure [1]
We present the results of 195Pt nuclear magnetic resonance (NMR) which is only measurable within the SP-charge density wave (CDW) phase boundary
The key results of this study were that the NMR spectral line shapes underwent fundamental changes passing from the low temperature—low low magnetic field singlet SP-CDW
Summary
The primary thrust of the work reported here concerns NMR (both spectra and spin-relaxation) on single crystal Per2[Pt(mnt)2] with a focus on the high magnetic field (2 to 33 T) dependence of the SP-CDW phases at low temperatures, and on the spectra over broad range of temperature above the SP-CDW ground state. A milestone in the understanding of the magnetic properties of the Per2[Pt(mnt)2] system in the higher temperature paramagnetic phase is the work of Bourbonnais et al [2] which addressed the temperature dependence of the 1H spin relaxation rate 1/T1 at 0.855 T from room temperature to ~ 4.2 K in a powdered sample. The conclusions of this work were that the formation of the CDW state is necessary to induce the SP transition, which otherwise would not form, and that the two order parameters remain coupled at least until the low temperature critical field of Bc ~ 20 T is reached
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