2015/05/31 by Jamie Brambleby, J. Brambleby, Paul Goddard +32 · 12 citations
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Atomic physics #Chemistry #Condensed matter physics #Crystal structure #Crystallography #Ground state #Isostructural #Magnetic moment #Magnetism in coordination complexes #Materials science #Neutron diffraction #Organic and Molecular Conductors Research #Physics #Pyrazine #Stereochemistry #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.92.134406
published in Physical Review B 92(13) (American Physical Society)
arxiv created 2015/09/04 · openalex publication_date 2015/10/07 · arxiv updated 2015/10/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
The magnetic ground state of two isostructural coordination polymers, (i) the quasi-two-dimensional S=1/2 square-lattice antiferromagnet [Cu(HF2)(pyrazine)2]SbF6 and (ii) a related compound [Co(HF2)(pyrazine)2]SbF6, was examined with neutron powder diffraction measurements. We find that the ordered moments of the Heisenberg S=1/2 Cu(II) ions in [Cu(HF2)(pyrazine)2]SbF6 are 0.6(1)\ensuremathμb, while the ordered moments for the Co(II) ions in [Co(HF2)(pyrazine)2]SbF6 are 3.02(6)\ensuremathμb. For Cu(II), this reduced moment indicates the presence of quantum fluctuations below the ordering temperature. We show from heat capacity and electron spin resonance measurements that due to the crystal electric field splitting of the S=3/2 Co(II) ions in [Co(HF2)(pyrazine)2]SbF6, this isostructual polymer also behaves as an effective spin-half magnet at low temperatures. The Co moments in [Co(HF2)(pyrazine)2]SbF6 show strong easy-axis anisotropy, neutron diffraction data, which do not support the presence of quantum fluctuations in the ground state, and heat capacity data, which are consistent with 2D or close to 3D spatial exchange anisotropy.