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We report the structural and magnetic properties of polycrystalline ferriferricyanide, Fe͓Fe͑CN͒ 6 ͔ •4H 2 O. The room temperature neutron diffraction pattern of the sample was refined with space group Fm3m by the Rietveld refinement technique. The Mössbauer spectrum of the sample at room temperature reveals the presence of low spin Fe 3+ ͑Fe LS , S =1/2͒ and high spin Fe 3+ ͑Fe HS , S =5/2͒ ions. The compound undergoes a paramagnetic to ferromagnetic phase transition at 17.4 K. Saturation magnetization at 2.3 K corresponds to parallel ordering of Fe HS and Fe LS spin only moments in Fe͓Fe͑CN͒ 6 ͔ •4H 2 O. Neutron diffraction study at 1.5 K shows the ordered site moments of 5.0͑2͒ and 0.8͑2͒ B for Fe HS and Fe LS ions, respectively, in Fe HS ͓Fe LS ͑CN͒ 6 ͔ •4H 2 O. The coercive field of the compound is an order of magnitude higher than that of many other compounds in the Prussian Blue analog family. The observed branching between field-cooled and zero field-cooled magnetization below T C ͑=17.4 K͒ is ascribed due to magnetic domain kinetics under different cooling conditions and the presence of available vacant sites in the lattice for the water molecules.

Magnetic properties of nanocrystalline La1-x MnO3+delta manganites: size effects V Markovich, I Fita, D Mogilyansky et al.Effect of size reduction on the structural and magnetic order in LaMnO3+delta (delta approx 0.03) nanocrystals: a neutron diffraction study Barnali Ghosh, V Siruguri, A K Raychaudhuri et al. Abstract. In this paper, we report an investigation of the ferromagnetic state and the nature of ferromagnetic transition of nanoparticles of La 0.67 Ca 0.33 MnO 3 using magnetic measurements and neutron diffraction. The investigation was performed on nanoparticles with crystal size down to 15 nm. The neutron data show that even down to a size of 15 nm the nanoparticles show finite spontaneous magnetization (M S ) although the value is much reduced compared to the bulk sample. We observed a non-monotonic variation of the ferromagneticto-paramagnetic transition temperature T C with size d and found that T C initially enhances upon size reduction, but for d < 50 nm it decreases again. The initial enhancement in T C was related to an increase in the bandwidth that occurred due to a compaction of the Mn-O bond length and a straightening of the Mn-O-Mn bond angle, as determined from the neutron data. The size reduction also changes the nature of the ferromagnetic-to-paramagnetic transition from first order to second order with critical exponents approaching mean field values. This was explained as arising from a truncation of the coherence length by the finite sample size.

We report an extraordinary coexistence of sign reversal of both magnetization and exchange bias field in the La0.2Ce0.8CrO3 nanoparticles. From the high resolution transmission electron microscopy image, and field dependence of thermoremanent and isothermoremanent magnetization measurements, the nanoparticles are found to be of core-shell nature. The core-shell configuration with an antiferromagnetic core of the Cr3+ and Ce3+ spins and a disordered shell with the uncompensated spins, explains the sign reversal of both magnetization and exchange bias field. The present study shows an excellent way of tuning the sign of both magnetization and exchange bias field in a single magnetic system.

A highly reversible (bipolar) switching of magnetization in a Prussian blue type molecular magnet Cu0.73Mn0.77[Fe(CN)6]⋅zH2O using low magnetic fields is demonstrated. The studied molecular compound also shows both positive and negative magnetocaloric effects below its magnetic ordering temperature. A molecular field theory calculation has also been done to explain the observed temperature dependent magnetization reversal behavior. Possible applications of the magnetic pole reversal phenomenon in magnetoelectronic and magnetocaloric devices such as magnetic memory and magnetic cooling/heating based constant temperature bath have been revealed.