01891nas a2200193   4500008004100000022001400041245013200055210006900187260007100256300001600327490000800343520112300351100001501474700001601489700001601505700003001521700001701551856012901568       2007                        eng d  a1932-744700aMagnetic transition and large magnetocaloric effect associated with surface spin disorder in Co and CocoreAgshell nanoparticles0 aMagnetic transition and large magnetocaloric effect associated w  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP  a14060-140660 v1113 a<p>We report a reversible, large magnetocaloric effect in the vicinity of a low-temperature magnetic transition in Co and CocoreAgshell nanoparticles synthesized using a wet chemical method. The as-synthesized assembly of the particles shows a sharp low-temperature peak in the zero-field-cooled (ZFC) magnetization well below the blocking transition temperature, and this feature is associated with the surface spin disorder. Co nanoparticles show a large increase in the magnetic entropy at around 15 K with a peak value of nearly 2.25 J/K center dot kg for an applied field of 30 kOe. A similar trend is also observed in the silver-coated Co particles. These are some of the largest NICE values observed in nanoparticles to date. The features are ascribed to the low-temperature spin-glass-like freezing transition associated with the surface spins in the shell region that is distinct from the behavior of core spins. Our studies reveal that manipulating the surface anisotropy in core-shell nanoparticles has the potential to lead to a large NICE effect and thus prove to be useful for magnetic refrigeration.</p>1 aPoddar, P.1 aSrinath, S.1 aGass, James1 aPrasad, Bhagavatula L. V.1 aSrikanth, H.  uhttps://library.ncl.res.in/content/magnetic-transition-and-large-magnetocaloric-effect-associated-surface-spin-disorder-co-001794nas a2200253   4500008004100000022001400041245006300055210006300118260009500181300001400276490000600290520093200296653002201228653002101250653002401271653003001295100001601325700001501341700002401356700003001380700001601410700001701426856009701443       2008                        eng d  a1533-488000aStatic and dynamic magnetic properties of Co nanoparticles0 aStatic and dynamic magnetic properties of Co nanoparticles  a25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USAbAMER SCIENTIFIC PUBLISHERScAUG  a4086-40910 v83 a<p>Co nanoparticles have been synthesized using wet-chemical methods. As-synthesized particles show a sharp low temperature peak in zero-field cooled (ZFC) magnetization well below the blocking transition temperature and this feature is associated with surface spin disorder. We have investigated the dynamic magnetic properties of Co using ac susceptibility and resonant RF transverse susceptibility (TS). We also studied the memory and relaxation effects in these nanoparticle systems. From these measurements we show a typical blocking behavior of an assembly of superparamagnetic nanoparticles with a wide distribution of blocking temperatures. The transverse susceptibility measurements on these particles show the presence of anisotropy even above the blocking temperature. The role of surface anisotropy and the size distribution of the particles on the observed memory and magnetic relaxation effects are discussed.</p>10aAc Susceptibility10aCo Nanoparticles10aMagnetic relaxation10aTransverse Susceptibility1 aSrinath, S.1 aPoddar, P.1 aSidhaye, Deepti, S.1 aPrasad, Bhagavatula L. V.1 aGass, James1 aSrikanth, H.  uhttps://library.ncl.res.in/content/static-and-dynamic-magnetic-properties-co-nanoparticles-001623nas a2200217   4500008004100000022001400041245012800055210006900183260007100252300001400323490000800337520078300345100002401128700002001152700001601172700001701188700001901205700001901224700003001243856013201273       2009                        eng d  a1932-744700aPreparation of nearly monodisperse nickel nanoparticles by a facile solution based methodology and their ordered assemblies0 aPreparation of nearly monodisperse nickel nanoparticles by a fac  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR  a3426-34290 v1133 a<p>Nickel nanoparticles have been synthesized by a simple wet chemical reduction technique in the presence of a surfactant sodium dodecyl sulfate (SDS) and a capping agent oleic acid. Varying the concentration of the surfactant and the capping agent has been found to critically govern the nature of the nanoparticles prepared. It is observed that at an optimum concentration of SDS and oleic acid, nearly monodisperse Ni nanoparticles are obtained that form highly ordered hexagonally close-packed structures on electron microscopy grids by a simple drop coating procedure. It is also shown that the presence of oleic acid is necessary for the stability of the Ni nanoparticles synthesized. Structural and magnetic characterizations of the nanoparticles are also presented.</p>1 aSidhaye, Deepti, S.1 aBala, Tanushree1 aSrinath, S.1 aSrikanth, H.1 aPoddar, Pankaj1 aSastry, Murali1 aPrasad, Bhagavatula L. V.  uhttps://library.ncl.res.in/content/preparation-nearly-monodisperse-nickel-nanoparticles-facile-solution-based-methodology-and-001545nas a2200229   4500008004100000022001400041245007800055210006900133260012500202300001100327490000800338520072000346100001501066700001401081700002001095700003001115700001501145700001601160700001701176700001701193856010501210       2010                        eng d  a0021-897900aField dependence of the magnetocaloric effect in core-shell nanoparticles0 aField dependence of the magnetocaloric effect in coreshell nanop  aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScMAY  a09A9020 v1073 a<p>The field dependence of the magnetic entropy change peak at the low temperature surface spin freezing transition in chemically synthesized, monodispersed Co, Co-Ag, and Ni-Ag core-shell nanoparticles is studied, with the aim of gaining insight into the critical exponents of this transition. It is evidenced that although the magnitude of the peak entropy change and position of the peak can be tuned by changing the composition and nature (metallic or organic) of the shell and surfactant layers, the characteristics of the spin freezing transition are not altered. The field dependence of the refrigerant capacity also confirms this finding. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3335514]</p>1 aFranco, V.1 aConde, A.1 aSidhaye, Deepti1 aPrasad, Bhagavatula L. V.1 aPoddar, P.1 aSrinath, S.1 aPhan, M., H.1 aSrikanth, H.  uhttps://library.ncl.res.in/content/field-dependence-magnetocaloric-effect-core-shell-nanoparticles-0