Tetrabutylammonium Salts of Aluminum(III) and Gallium(III) Phthalocyanine Radical Anions Bonded with Fluoren‐9‐olato− Anions and Indium(III) Phthalocyanine Bromide Radical Anions

Reduction of aluminum(III), gallium(III), and indium(III) phthalocyanine chlorides by sodium fluorenone ketyl in the presence of tetrabutylammonium cations yielded crystalline salts of the type (Bu₄N⁺)₂[M^III(HFl−O⁻)(Pc^.3−)]^.−(Br⁻) ⋅ 1.5 C₆H₄Cl₂ [M=Al ( 1 ), Ga ( 2 ); HFl−O⁻=fluoren‐9‐olato⁻ anion; Pc=phthalocyanine] and (Bu₄N⁺) [In^IIIBr(Pc^.3−)]^.− ⋅ 0.875 C₆H₄Cl₂ ⋅ 0.125 C₆H₁₄ ( 3 ). The salts were found to contain Pc^.3− radical anions with negatively charged phthalocyanine macrocycles, as evidenced by the presence of intense bands of Pc^.3− in the near‐IR region and a noticeable blueshift in both the Q and Soret bands of phthalocyanine. The metal(III) atoms coordinate HFl−O⁻ anions in 1 and 2 with short Al−O and Ga−O bond lengths of 1.749(2) and 1.836(6) Å, respectively. The C−O bonds [1.402(3) and 1.391(11) Å in 1 and 2 , respectively] in the HFl−O⁻ anions are longer than the same bond in the fluorenone ketyl (1.27–1.31 Å). Salts 1 – 3 show effective magnetic moments of 1.72, 1.66, and 1.79 μ_B at 300 K, respectively, owing to the presence of unpaired S= 1/2 spins on Pc^.3−. These spins are coupled antiferromagnetically with Weiss temperatures of −22, −14, and −30 K for 1 – 3 , respectively. Coupling can occur in the corrugated two‐dimensional phthalocyanine layers of 1 and 2 with an exchange interaction of J /k _B=−0.9 and −1.1 K, respectively, and in the π‐stacking {[In^IIIBr(Pc^.3−)]^.−}₂ dimers of 3 with an exchange interaction of J /k _B=−10.8 K. The salts show intense electron paramagnetic resonance (EPR) signals attributed to Pc^.3−. It was found that increasing the size of the central metal atom strongly broadened these EPR signals.     

Antiferromagnetically coupled multilayers of (Co90Fe10 tF/Ru tRu)×N and (Ni81Fe19 tF/Ru tRu)×N prepared by ion beam deposition

This work describes multilayers of Co₉₀Fe₁₀ t_F/Ru t_Ru/Co₉₀Fe₁₀ t_F and Ni₈₁Fe₁₉ t_F/Ru t_Ru/Ni₈₁Fe₁₉ t_F (20 Åt_F200 Å) prepared at ambient temperature by ion beam deposition on Si/SiO₂ 3 kÅ substrates. The samples exhibited a maximum antiferromagnetic coupling with t_Ru=3.2 Å and M–H curves characterized by zero remanent magnetic moment and enhanced saturation field. Antiferromagnetic peaks were present with t_Ru17 and 30 Å.     

铁磁/反铁磁双层薄膜自旋波共振谱

本文在一维海森堡模型的基础上,采用界面参数化方法,研究了铁磁/反铁磁双层薄膜中自旋波低温激发问题．重点讨论了表面各向异性对薄膜中自旋波共振谱的影响．结果表明：体系中的自旋波本征模存在共振行为,表面各向异性场对体模、完全禁闭模的共振谱影响较大,对界面模没有影响．     

Oscillation of coercivity between positive and negative in MnxGe1-x：H ferromagnetic semiconductor films

Amorphous MnxGe1-x :H ferromagnetic semiconductor films prepared in mixed Ar with 20% H2 by magnetron cosputtering show global ferromagnetism with positive coercivity at low temperatures. With increasing temperature, the coercivity of MnxGe1-x :H films first changes from positive to negative, and then back to positive again, which was not found in the corresponding MnxGe1-x and other ferromagnetic semiconductors before. For Mn0.4Ge0.6 :H film, the inverted Hall loop is also observed at 30 K, which is consistent with the negative coercivity. The negative coercivity is explained by the antiferromagnetic exchange coupling between the H-rich ferromagnetic regions separated by the H-poor non-ferromagnetic spacers. Hydrogenation is a useful method to tune the magnetic properties of MnxGe1-x films for the application in spintronics.     

Magnetic brillouin zone effect on the resistivity of semimetallic-like fermi surface in USb

To probe the effect of the protein environment on the retinal chromophore of rhodopsin, we performed molecular dynamics simulations using combined quantum mechanics/molecular mechanics (QM/MM). The starting geometry of the protein is based on the 2.6Å X-ray structure of bovine rhodopsin of Okada et al. [T. Okada, et al. Proc. Natl. Acad. Sci. USA 99 5982 (2002)]. The wild-type chromophore of rhodopsin according to our calculations shows a highly twisted conformation around the central region, from C10 to C13, due to non-bonded interaction with the protein pocket. The absolute sense of twist of the C11–C12 and C12–C13 bonds is negative (?19 ± 9°) and positive (170 ± 8°), respectively. The 13-demethyl retinal chromophore, in which the methyl group at the C13 position is removed, is less distorted in this region. The C11–C12 bond is less twisted (?15 ± 10°) and the C12–C13 bond is planar (179 ± 9°) . The flattened geometry of this artificial chromophore is supported by spectroscopic evidence.     

Neutron powder diffraction studies in CaMn1‐xCuxO3 (x = 0, 0.2)

Neutron powder diffraction patterns were recorded on CaMn_1‐xCu_xO₃ (x = 0 and 0.20) compounds at different temperatures down to 11K. All the patterns were analyzed by employing Rietveld refinement technique and using the Fullprof program. The observed crystallographic peaks could be refined by using Pbnm space group and no structural transition has been observed down to 11K. An additional peak at 2θ = 16.7° has been observed with decrease in temperature below T_N and its intensity was found to increase with decrease in temperature. It could be indexed to magnetic (101) plane. The magnetic ordering is found to be G‐type antiferromagnetic behaviour. The magnetic moment at 11K for the samples x = 0.0 and 0.20 are found to be 2.69 and 2.42μ_B. The doped Cu ions are found to be in Cu²⁺ state and take part antiferromagnetic interactions with Mn ions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

反铁磁耦合记录介质的一级翻转曲线

用实验测量和微磁计算的方法得到了反铁磁耦合记录介质的一级翻转曲线.利用微磁计算的目的是便于正确地理解一级翻转曲线分布图.因为它可以把一级翻转曲线分布图中不同部分与相应的磁化翻转联系起来.这样一级翻转曲线就能被用来分析复杂磁化翻转及其相互作用的细节,而这种手段可以提供比通常用的ΔM方法更多的信息. 关键词： 反铁磁耦合记录介质 一级翻转曲线 微磁学模拟     

Electronic Structure Modulation in an Exceptionally Stable Non‐Heme Nitrosyl Iron(II) Spin‐Crossover Complex

The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF₆)₂ (bztpen=N‐benzyl‐N,N′,N′‐tris(2‐pyridylmethyl)ethylenediamine) displays an S=1/2?S=3/2 spin crossover (SCO) behavior (T_1/2=370 K, ΔH=12.48 kJ mol^?1, ΔS=33 J K^?1 mol^?1) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0?S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120–420 K affording a detailed picture of how the electronic distribution of the t_2g–e_g orbitals modulates the structure of the {FeNO}⁷ bond, providing valuable magneto–structural and spectroscopic correlations and DFT analysis.     

Synthesis,crystal structure and magnetic properties of diaquabis(2,6‐diamino‐7H‐purin‐1‐ium‐κN9)bis(4,4′‐oxydibenzoato‐κO)cobalt(II) dihydrate

The title mononuclear Co^II complex, [Co(C₅H₇N₆)₂(C₁₄H₈O₅)₂(H₂O)₂]·2H₂O, has been synthesized and its crystal structure determined by X‐ray diffraction. The complex crystallizes in the triclinic space group P, with one formula unit per cell (Z = 1 and Z′ = ). It consists of a mononuclear unit with the Co^II ion on an inversion centre coordinated by two 2,6‐diamino‐7H‐purin‐1‐ium cations, two 4,4′‐oxydibenzoate anions (in a nonbridging κO‐monodentate coordination mode, which is less common for the anion in its Co^II complexes) and two water molecules, defining an octahedral environment around the metal atom. There is a rich assortment of nonbonding interactions, among which a strong N⁺—H…O⁻ bridge, with a short N…O distance of 2.5272 (18) Å, stands out, with the H atom ostensibly displaced away from its expected position at the donor side, towards the acceptor. The complex molecules assemble into a three‐dimensional hydrogen‐bonded network. A variable‐temperature magnetic study between 2 and 300 K reveals an orbital contribution to the magnetic moment and a weak antiferromagnetic interaction between Co^II centres as the temperature decreases. The model leads to the following values: A (crystal field strength) = 1.81, λ (spin‐orbit coupling) = −59.9 cm⁻¹, g (Landé factor) = 2.58 and zJ (exchange coupling) = −0.5 cm⁻¹.     

Absence of phase transition for antiferromagnetic Potts models via the Dobrushin uniqueness theorem

We prove that theq-state Potts antiferromagnet on a lattice of maximum coordination numberr exhibits exponential decay of correlations uniformly at all temperatures (including zero temperature) wheneverq>2r. We also prove slightly better bounds for several two-dimensional lattices: square lattice (exponential decay forq7), triangular lattice (q11), hexagonal lattice (q4), and Kagomé lattice (q6). The proofs are based on the Dobrushin uniqueness theorem.