Novel Magnetism in Prussian Blue based Molecular Magnetic Compounds

Orateur : S. M. YUSUF (Solid State Physics Division - Bhabha Atomic research Centre - Mumbai - India)

Inorganic molecular magnetic materials with spins on metal ions, and the exchange pathway provided by the organic radicals that do not contain spin have drawn a special attention. The most important compounds in this category belong to Prussian Blue family having general formula ZyAn[B(CN)6]m.x(H2O) where A and B are the transition or rare earth metal ions, and Z is a monovalant cation. We have observed the phenomenon of magnetic pole reversal in multi-metal Prussian blue type molecular magnetic compounds (CuxMn1-x)1.5[Fe(CN)6].zH2O. The microscopic mechanism of the observed negative magnetization has been understood using Rietveld analysis and reverse Monte Carlo simulation of the neutron diffraction data. The temperature variation of net magnetization, obtained from the molecular field theory calculation, agrees very well with the observed magnetization reversal. The effect of an external magnetic field on the magnetization reversal has also been studied. A highly reversible-bipolar switching of magnetization using low applied magnetic fields is demonstrated. Our work has shown that the observed bipolar switching of magnetization can have novel applications in (i) volatile magnetic memory technology, (ii) thermo-magnetic switches, and (iii) a self-driven constant temperature bath. Besides, our work exploiting neutron diffraction on other Prussian Blue analogues has highlighted the role of structural defects, namely, vacancies of B(CN)6 B = Fe, Cr and non-coordinated water molecules, and quenched disorder in controlling magnetism. Very recently, magnetic field driven transition from an antiferromagnetic ground state to a ferrimagnetic state in (Rb/Ba/Mn)[Fe(CN)6].0.48H2O Prussian blue analogue has been elucidated. The dynamical behaviour of water molecules in Cu0:75Mn0:75[Fe(CN)6].7H2O molecular magnet has been brought out by performing a quasielastic neutron scattering study. In my talk, some of these results will be presented in the light of importance of the studied molecular magnets for their practical applications.

Télécharger dans mon agenda