Source of magnetic anisotropy in quasi-two-dimensional XY {Cu-4(tetrenH(5))W(CN)(8)](4).7.2H(2)O)}(n) bilayer molecular magnet

Article

关键词: POLARIZED NEUTRON-DIFFRACTION;    SPIN CORRELATIONS;    CRYSTAL-STRUCTURE;    CU-II;    MO;    SUSCEPTIBILITY;    SYSTEMS;    2D;   

DOI  :  10.1103/PhysRevB.87.024406

来源: SCIE

【 摘 要 】

To identify the origin of the XY spin dimensionality in the bilayered system {Cu-4(tetrenH(5))[W(CN)(8)](4). 7.2H(2)O}(n) (WCuT) we use a combination of single-crystal experiments (bulk magnetization, neutron flipping ratio, electron magnetic resonance, neutron diffraction) and theoretical modeling (exchange-charge model of the crystal field, dipolar energy, and density functional calculations). Our experiments show that the magnetic properties of WCuT are anisotropic and two-dimensional correlations build up below 70 K. The hard anisotropy axis is perpendicular to the layers (b axis) and a small anisotropy within the ac layers is present. Modeling of the crystal field validates treatment of tungsten and copper as spin S = 1/2 ions with anisotropic g values. The local magnetic anisotropy results from the common action of the crystal field and spin-orbit coupling and is along the c axis for both ions. Density functional calculations identify the origin of the ferromagnetic exchange in different energies and symmetries of the tungsten- and copper-dominated orbitals and anticipate different exchange couplings across the apical (along the b axis) and equatorial (in the ac plane) Cu-CN-W bridges due to difference in the hybridization efficiency. Calculation of the dipolar energy for various spin configurations suggests that dipolar interactions play a decisive role in the ac-planar anisotropy in this system. We propose that the effective XY spin dimensionality in WCuT is established by a combination of the axial local anisotropy of the W and Cu ions and the long-range magnetic dipolar interactions on the bilayered square lattice. DOI: 10.1103/PhysRevB.87.024406

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