Modeling of the magnetic susceptibilities of the ambient- and high-pressure phases of(VO)2P2

Abstract

The magnetic susceptibilities χ versus temperature T of powders and single crystals of the ambient-pressure (AP) and high-pressure (HP) phases of (VO)2P2O7 are analyzed using an accurate theoretical prediction of χ(T, J1, J2) for the spin-1/2 antiferromagnetic alternating-exchange (J1, J2) Heisenberg chain. The results are consistent with recent models with two distinct types of alternating-exchange chains in the AP phase and a single type in the HP phase. The spin gap for each type of chain is derived from the respective set of two fitted alternating exchange constants and the one-magnon dispersion relation for each of the two types of chains in the AP phase is predicted. The influences of interchain coupling on the derived intrachain exchange constants, spin gaps, and dispersion relations are estimated using a mean-field approximation for the interchain coupling. The accuracies of the spin gaps obtained using fits to the low-T χ(T ) data by theoretical low-T approximations are determined. The results of these studies are compared with previously reported estimates of the exchange couplings and spin gaps in the AP and HP phases and with the magnon dispersion relations in the AP phase measured previously using inelastic neutron scattering.

Single-crystal growth, crystallography, magnetic susceptibility, heat capacity, and thermal expansion of the antiferromagneticS=1chain compoundCaV2ONiazi1, Bud’ko2, Schlagel3 et al. 2009Phys. Rev. BSelf Cite333550View full textAdd to dashboardCite

“…The chiral phase implies a helical spin arrangement in contrast to the collinear spin models proposed 13 in the neutron diffraction study. Furthermore, the observation of a 51 V nuclear resonance at the normal 51 V Larmor frequency 10,11 at temperatures at and below 4 K is not consistent with the long-range antiferromagnetic ordering found at 4 K from the neutron diffraction measurements 13 since such ordering produces a very large static local magnetic field of order 20 T at the positions of the V nuclei.…”

“…10,11 In single crystals, at temperatures below 45 K we do find a zero-field 51 V NMR signal where the 51 V nuclei resonate in the static component of the local magnetic field generated by the long-range AF order below T N Ϸ 70 K. 14 The ordered moment at 4.2 K in the crystals was estimated from the zero-field 51 V NMR measurements to be 1.3͑3͒ B / ͑V atom͒, somewhat larger than but still consistent with the value 1.06͑6͒ B / ͑V atom͒ from the above neutron diffraction measurements. 13 An energy gap ⌬ for antiferromagnetic spin wave excitations was found with a value ⌬ / k B =80͑20͒ K in the temperature range of 4-45 K, where k B is Boltzmann's constant.…”

“…A good example of this fact arose in the study of the antiferromagnetic alternating exchange chain compound vanadyl pyrophosphate, ͑VO͒ 2 P 2 O 2 , the history of which is described in detail in the introduction in Ref. 51. The ultimate arbiter of the validity of a spin model is inelastic neutron scattering measurements of the magnetic excitation dispersion relations in single crystals.…”

Structural and magnetic dimers in the spin-gapped systemCuTe2O5

“…The singlet-forming Cu 2+ ions in CaCuGe 2 O 6 are given by the third-nearest-neighbor copper pairs that occur between chains of edge-sharing distorted CuO6 octahedra. 35,36 Both alternating chain and spin ladder models describe the magnetic susceptibility of (VO) 2 P 2 O 7 well, 37,38,39 but an alternating chain model was proven to be correct for (VO) 2 P 2 O 7 by neutron scattering experiments 40 on oriented single crystals and also by spin dimer analysis based on EHTB calculations. 41 All these examples demonstrate the importance of considering the overlap between magnetic orbitals in arriving at a correct spin lattice model.…”

Synthesis and structural, magnetic, thermal, and transport properties of several transition metal oxides and aresnides

“…A good example of this fact arose in the study of the antiferromagnetic alternating exchange chain compound vanadyl pryophosphate, (VO) 2 P 2 O 2 , the history of which is described in detail in the introduction of Ref. [186]. The ultimate arbiter of the validity of a spin model is inelastic neutron scattering measurements of the magnetic excitation dispersion relations in single crystals.…”