Chibotaru, L.F.

Gredin, P.

Kirilenko, Demid

Mortier, M.

Moshchalkov, V.V.

Schildermans, N.

Tikhomirov, V.K.

van den Heuvel, W.

Van Tendeloo, Gustaaf

Vanacken, J.

Abstract: The magnetization of luminescent Er3+-doped PbF2 nanoparticles (formula Er0.3Pb0.7F2.3) has been studied. Despite the high concentration of the doping Er3+ ions and relatively large size (8 nm) of these nanoparticles we have found no deviation between field-cooled and zero-field-cooled magnetization curves down to T=0.35\u2002K, which points out an ultralow blocking temperature for the reversal of magnetization. We also have found strongly deviating magnetization curves M(H/T) for different temperatures T. These results altogether show that the investigated nanoparticles are not superparamagnetic, but rather each Er3+ ion in these nanoparticles is found in a paramagnetic state down to very low temperatures, which implies the breakdown of the N\ue9el-Brown giant spin model in the case of these nanoparticles. Calculations of magnetization within a paramagnetic model of noninteracting Er3+ ions completely support this conclusion. Due to the ultralow blocking temperature, these nanoparticles have a potential for magnetic field-induced nanoscale refrigeration with an option of their optical localization and temperature control

Institutional Repository Universiteit Antwerpen

Ultralow blocking temperature and breakdown of the giant spin model in <tex>Er^{3+}$</tex>-doped nanoparticles

Ultralow blocking temperature and breakdown of the giant spin model in <tex>Er^{3+}$</tex>-doped nanoparticles

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Institutional Repository Universiteit Antwerpen