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Field induced single molecule magnet behavior in Dy-based coordination polymer

A new mononuclear Dysprosium based Coordination Polymer {Dy-CP} was investigated magnetically using dc and ac magnetic susceptibility. The dc magnetic susceptibility does not exhibit any long-range ordering down to 1.8 K and the negative value of Curie Constant (~ - 4 K) indicate the dominance of antiferromagnetic interactions between the Dy (III) spins. Ac susceptibility exhibits absence of single molecular magnet behavior at zero dc magnetic field and shows signal of quantum tunneling magnetization (QTM) below 8 K. However, on the superimposition of dc magnetic field (3 kOe), frequency dependent relaxation peak emerged at T_f = 5 K and QTM signal suppress at higher fields. The intermediate value of Mydosh parameter calculated from the shift in peak position (T_f) in ac susceptibility reflects the formation of superparamagnetic state. Further, the temperature dependence of Tf is analyzed with Arrhenius and Cole-Cole plot. The magnetic susceptibility analysis yields characteristics pre-relaxation factor 1.40x10^(-12) sec and energy barrier ΔE/k_B = 93.4 K, indicating the slow spin relaxation. The Cole-Cole fit to the ac susceptibility data shows further evidence for the single ion spin relaxation. Thus, the magnetic measurements support the single-molecule magnet behavior in Dy-CP under the application of dc magnetic field.