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-002133nas a2200253   4500008004100000245009100041210006900132260000800201300001300209490000800222520132700230653001301557653001901570653005201589653002601641653002301667100001701690700001601707700001201723700001501735700002001750700001901770856009001789       2017                        eng d00aMagnetic studies of SiO<inf>2</inf> coated CoFe<inf>2</inf>O<inf>4</inf> nanoparticles0 aMagnetic studies of SiOinf2inf coated CoFeinf2infOinf4inf nanopa  cNOV  a 683-6900 v4413 aOleic acid capped CoFe2O4 nanoparticles which exhibit a high coercivity of ∼9.47 kOe at room temperature were coated with a robust coating of SiO2. We have used chemical synthesis method to obtain SiO2 coated CoFe2O4 nanoparticles with different weight percentages of CoFe2O4 in SiO2 (1.5, 3.1 and 4.8 wt.%). The morphological investigation of the coated nanoparticles by transmission electron microscopy shows that the particles are spherical with average size ∼160 nm. Infrared spectroscopy reveals that oleic acid capping on the surface of CoFe2O4 nanoparticles is retained after silica coating process. The complete coating of SiO2 on CoFe2O4 nanoparticles is confirmed by X-ray photoelectron spectroscopy as there is no signature of cobalt or iron ions on the surface. Magnetic measurements show that coercivity of SiO2 coated CoFe2O4 particles remains more or less unaffected as in CoFe2O4 nanoparticles at room temperature. In addition, the temperature dependent magnetic measurements show that at 5 K the CoFe2O4 and SiO2 coated 1.5 wt.% CoFe2O4 samples exhibit a very high value of coercivity (∼20 kOe) which is more than twice as compared to room temperature coercivity value (∼9.47 kOe). We conclude that silica coating in our study does not significantly affect the coercivity of CoFe2O4 nanoparticles.10aCoatings10acoercive force10aHigh Resolution Transmission Elctron Microscopy10ainfrared spectroscopy10aMagnetic materials1 aLimaye, M.V.1 aSingh, S.B.1 aDas, R.1 aPoddar, P.1 aAbyaneh, M., K.1 aKulkarni, S.K.  uhttps://library.ncl.res.in/content/magnetic-studies-sio2-coated-cofe2o4-nanoparticles