Stepwise synthesis and magnetic control of trimetallic magnets [Co2Ln(L)2(H2O)4][Cr(CN)6].nH2O (Ln = La, Gd; H2L = 2,6-Di(acetoacetyl)pyridine) with 3-D pillared-layer structure

Integration of mononuclear [Cr(CN)6]3- and preorganized trinuclear [Co2Ln(L)2]3+ complexes provides novel trimetallic magnets having a 3-D pillared-layer framework with an alternate array of 2-D layer extended by Cr(III)-CN-Co(II) linkages and Ln(III) ion. The overall magnetic nature can be systematically controlled by Ln(III) ions inserted between the 2-D ferromagnetic layers.     

A three-dimensional ferromagnet, [Ni(dipn)]3[Cr(CN)6]2.3H2O (dipn = dipropylene triamine), based on a cubic Cr8Ni12 unit

The combination of Ni2+, dipropylenetriamine (dipn), and [Cr(CN)6]3- affords the cyanide-bridged bimetallic assembly, [Ni(dipn)]3[Cr(CN)6]2.3H2O (1). This compound crystallizes in cubic space group Pa, with a = b = c = 20.9742(7) A and Z = 8. A three-dimensional network is constructed on the basis of a Cr8Ni12 cubane unit formed by an alternate array of [Cr(CN)6]3- and [Ni(dipn)]2+ units through Cr-CN-Ni-NC-Cr edges. Cryomagnetic studies reveal a ferromagnetic interaction between Cr(III) and Ni(II) ions and a long-range ferromagnetic ordering below 42 K with very small coercive field. To the best of our knowledge, this compound is the first "complete ferromagnet" providing three-dimensional ferromagnetic interaction through a three-dimensional bridging structure that is based on a cubic unit among general metal-oxide and molecule-based magnets. Magnetooptical studies demonstrate a strong correlation between magnetic and optical properties.     

Dynamical quark effects on light quark masses

Light quark masses are calculated in lattice QCD with two degenerate flavors of dynamical quarks. The calculations are made with improved actions with lattice spacing a = 0.22-0.11 fm. In the continuum limit we find m(M&Smacr;)(ud)(2 GeV) = 3.44(+0.14)(-0.22) MeV using the pi and rho meson masses as physical input, and m(M&Smacr;)(s)(2 GeV) = 88(+4)(-6) MeV or 90(+5)(-11) MeV with the K or straight phi meson mass as additional input. The quoted errors represent statistical and systematic combined, the latter including those from continuum and chiral extrapolations, and from renormalization factors. Compared to quenched results, two flavors of dynamical quarks reduce quark masses by about 25%.     

B(0)-B(0) mixing in unquenched lattice QCD

We present an unquenched lattice calculation for the B(0)-B(0) transition amplitude. The calculation, carried out at an inverse lattice spacing 1/a=2.22(4) GeV, incorporates two flavors of dynamical quarks described by the O(a)-improved Wilson fermion action and heavy quarks described by nonrelativistic QCD. Particular attention is paid to the uncertainty that arises from the chiral extrapolation, especially the effect of pion loops, for light quarks, which we find could be sizable for the leptonic decay constant, whereas it is small for the B parameters. We obtain f(B(d))=191(10)(+12-22) MeV, f(B(s))/f(B(d))=1.13(3)(+13-2), B(B(d))(m(b))=0.836(27)(+56-62), B(B(s))/B(B(d))=1.017(16)(+56-17), and xi=1.14(3)(+13-2), where the first error is statistical, and the second is systematic, including uncertainties due to chiral extrapolation, finite lattice spacing, heavy quark expansion, and perturbative operator matching.