Magnetic relaxation versus 3D long-range ordering in {Dy2Ba(alpha-fur)(8)}(n) furoate polymers.

A novel Dy-complex formulated as {[Dy2Ba(alpha-C4H3OCOO)(8)center dot(H2O)(4)]center dot 2H(2)O}(n’) {Dy2Ba(alpha-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 alpha-furoate ligands consolidate 1D zig-zag chains formed by Dy-2 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) approximate to J”/k(B) = +0.55 K. In the absence of an applied magnetic field, the dynamic relaxation of the magnetization occurs through the fast (tau(T) similar to 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) approximate to 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 tau(0) similar to 10(-9) s at H = 2 kOe) and a very slow (tau(s) similar to 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.