title: Large magnetocaloric effect, moment, and coercivity enhancement after coating Ni nanoparticles with Ag.
abstract: We observe a large magnetocaloric effect in monodisperse Ni and Ni(core)Ag(shell) nanoparticles in the superparamagnetic region. The organically passivated Ni nanospheres show a large magnetic entropy change of 0.9 J kg(-1)  K for a 3 T magnetic field change. In comparison to the surfactant-coated Ni nanoparticles, the Ni(core)Ag(shell) nanoparticles show an enhanced coercivity, magnetization, and magnetocaloric effect (1.3 kg K for a 3 T magnetic field change). The coercivity at 10 K increases from 360 Oe for Ni nanoparticles to nearly 610 Oe for Ni(core)Ag(shell) particles. This large enhancement is attributed to the enhanced inter-particle interaction, which is mediated by the metallic shell, over the relatively weaker dipolar interaction in the surfactant-coated Ni nanoparticles, and to modification of the surface spin structure.
authors.affiliation: School of Physics, University of Hyderabad, Hyderabad 500046 (India).
authors.forename: Sanyadanam
authors.initials: S
authors.lastname: Srinath
authors.forename: Pankaj
authors.initials: P
authors.lastname: Poddar
authors.forename: Raja
authors.initials: R
authors.lastname: Das
authors.forename: Deepti
authors.initials: D
authors.lastname: Sidhaye
authors.forename: Bhagavatula Lakshmi Vara
authors.initials: BL
authors.lastname: Prasad
authors.forename: James
authors.initials: J
authors.lastname: Gass
authors.forename: Hariharan
authors.initials: H
authors.lastname: Srikanth
keywords: anisotropy; core-shell; magnetic properties; nanoparticles; superparamagnetic