Bartolomé E, Bartolomé J, Melnic S, Prodius D, Shova S, Arauzo A, Luzón J, Badía-Romano L, Luis F, Turta C
Escola Universitària Salesiana de Sarrià (EUSS), Passeig Sant Joan Bosco 74, 08017-Barcelona, Spain.
Dalton Trans. 2014 Jul 28;43(28):10999-1013. doi: 10.1039/c4dt00538d.
A novel Dy-complex formulated as {[Dy2Ba(α-C4H3OCOO)8·(H2O)4]·2H2O}n, {Dy2Ba(α-fur)8}n, has been synthesized, structurally characterized, and magnetically and thermally investigated as a function of field and temperature, down to 85 mK. The α-furoate ligands consolidate 1D zig-zag chains formed by Dy2 dimers separated by Ba ions. Ab initio calculations were used to determine the easy anisotropy axis direction, the gyromagnetic tensor components and the energy levels of each Dy. The heat capacity and susceptibility measurements allowed us to conclude that intradimer and interdimer interactions are ferromagnetic and of the same order, J'/k(B) ≈ J''/k(B) = +0.55 K. In the absence of an applied magnetic field, the dynamic relaxation of the magnetization occurs through the fast (τ(T) ~ 10(-5) s) spin-reversal of each of the individual Dys through a quantum tunneling (QT) process. A long-range 3D ordered state is achieved at T(N) = 0.25 K, in which the ferromagnetically coupled zig-zag chains (J'/k(B) ≈ J''/k(B) = +0.528(1) K) running along the c-axis are antiferromagnetically coupled to the adjacent chains (J'''/k(B) = -0.021(1) K). Critical slowing down of the QT time constant is observed when the temperature approaches T(N). Under the application of a magnetic field, the QT relaxation is replaced by an Orbach process (with energy barrier U/k(B) = 68 K and τ0 ~ 10(-9) s at H = 2 kOe) and a very slow (τ(s) ∼ 0.2 s) relaxation process. We propose and demonstrate the proof of concept of a spintronic device, in which two different relaxation rates can be selected, and on/off switched by magnetic field biasing. The dynamical behavior of this compound is compared with another furoate to discuss the effect of competitive interactions.
已合成一种新颖的镝配合物，其化学式为{[Dy₂Ba(α-C₄H₃OCOO)₈·(H₂O)₄]·2H₂O}ₙ，即{Dy₂Ba(α-糠酸酯)₈}ₙ，并对其进行了结构表征，还研究了其在磁场和温度作用下直至85 mK的磁性和热性质。α-糠酸酯配体巩固了由钡离子分隔的Dy₂二聚体形成的一维之字形链。采用从头算计算来确定每个Dy的易各向异性轴方向、旋磁张量分量和能级。热容和磁化率测量使我们得出结论，二聚体内和二聚体间的相互作用是铁磁性的且量级相同，J'/k(B) ≈ J''/k(B) = +0.55 K。在无外加磁场时，磁化强度的动态弛豫通过每个单独的Dy的快速（τ(T) ~ 10⁻⁵ s）自旋反转，经由量子隧穿（QT）过程发生。在T(N) = 0.25 K时实现了长程三维有序态，其中沿c轴排列的铁磁耦合之字形链（J'/k(B) ≈ J''/k(B) = +0.528(1) K）与相邻链反铁磁耦合（J'''/k(B) = -0.021(1) K）。当温度接近T(N)时，观察到QT时间常数的临界慢化。在施加磁场时，QT弛豫被一个奥巴赫过程（在H = 2 kOe时能垒U/k(B) = 68 K且τ₀ ~ 10⁻⁹ s）和一个非常缓慢（τ(s) ∼ 0.2 s）的弛豫过程所取代。我们提出并证明了一种自旋电子器件的概念验证，其中可以选择两种不同的弛豫速率，并通过磁场偏置进行开/关切换。将该化合物的动力学行为与另一种糠酸酯进行比较，以讨论竞争相互作用的影响。
