Current activities on low dimensional magnetism and magnetization reversal phenomenon

We have carried out in-depth investigations of several classes of magnetic materials and magnetic phenomena by employing powerful neutron scattering techniques. We have successfully employed the neutron diffraction technique to reveal nature of magnetic ground states of a large variety of spin systems with reduced space dimensions, such as Ca₃Co₂O₆, (CuBr)Sr₂Nb₃O₁₀, Zn₂VO(PO₄)₂, CaNi₃P₄O₁₄, Ca_2.5-xLa_xSr_0.5GaMn₂O₈, Na₂Co₂TeO₆, Na₂Ni₂TeO₆, Na₂Cu₃Ge₄O₁₂, Bi₃FeMo₂O₁₂, Na₂Mn₃O₇, YBaCo_4-xFe_xO₇, barlowite (Cu₄(OH)₆FBr), Co^II-MOF, Ba₂Ni(PO₄)₂, Ba₂Mn(PO₄)₂, ((M(Δ)(Δ))(ox)₂(phen)₂)_n (M: Fe/Mn), and ((Cu₃(CO)3)₂(bpe)₃)·2ClO₄)n. The reverse Monte Carlo (RMC) simulation method of neutron diffraction data modelling and the Rietveld refinement for magnetic structure-analysis are employed to quantify short-range as well as long-range magnetic correlations. Recently, we have also investigated magnetic excitations of many such spin systems by employing inelastic neutron scattering. The phenomenon of negative magnetization (or magnetization reversal) is another topic of our current interest that has been investigated in several ferrimagnetically ordered systems, such as Prussian blue-type molecular magnets (PBAs), Cr-based oxide nanoparticles, perovskites, viz. NdMnO₃, Li_0.5FeCr_1.5O₄, La_0.5Pr_0.5CrO₃, and YbCrO₃, spinels CoCr₂-xFexO₄, and garnet Ho₃Fe₅O₁₂. In my talk, I shall give an overview of the recent results, and highlight the physics that is responsible for novel magnetic ground states in such low dimensional spin systems, and negative magnetization materials. (author)