Nanoscopic molecular cluster V15 high-field PER and magnetization at ultra-low temperatures
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TARANTUL, Alex, MULLER, Achim, ȚUKERBLAT, Boris S.. Nanoscopic molecular cluster V15 high-field PER and magnetization at ultra-low temperatures. In: Chemistry Journal of Moldova, 2007, nr. 1(2), pp. 17-35. ISSN 1857-1727.
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Chemistry Journal of Moldova
Numărul 1(2) / 2007 / ISSN 1857-1727 /ISSNe 2345-1688

Nanoscopic molecular cluster V15 high-field PER and magnetization at ultra-low temperatures

Pag. 17-35

Tarantul Alex, Muller Achim, Țukerblat Boris S.
 
 
Disponibil în IBN: 11 decembrie 2013


Rezumat

In this paper we give a short overview of our efforts in the understanding of the magnetic properties of the fascinating nanoscopic cluster K6[VIV 15As6 O42(H2 O)]·8H2 O (here after V15) exhibiting layers of magnetization. We analyze EPR and adiabatic magnetization of the V15 cluster with a triangular VIV 3 array causing spin frustration. A model for V15 includes isotropic and antisymmetric (AS) exchange interactions in the general form compatible with the trigonal symmetry. Orientation of the AS vector (but not only its absolute value) is shown to play an important physical role in spin-frustrated systems. We were able to reach perfect fit to the experimental data on the stepwise dependence of magnetization vs. field at ultra-low temperatures. Furthermore, it was possible for the first time to estimate precisely two components of the AS vector coupling constant, namely, in-plane component and the perpendicular part. We show that only intramultiplet transitions in EPR are allowed when the vector of AS exchange is normal to the plane of vanadium triangle, mean while the in-plane part of AS exchange gives rise to a series of weak intermultiplet transitions. Experimental data on high-frequency EPR of V15 at low temperatures are discussed. The spin-vibronic effects in trimeric spin frustrated clusters are also studied and an important role of the interplay between the AS exchange and Jahn-Teller interaction is revealed. The results clarify the concept of spin-frustration in view of its magnetic and spectroscopic manifestations in metal clusters.

Cuvinte-cheie
nanoscopic molecular magnets; V15 cluster; antisymmetric exchange; Jahn- Teller effect