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Paramagnetic-superparamagnetic transition in molecular-sieve-supported antiferromagnetic particles

Lazaro, FJ; Lopez, A; Larrea, A; Pankhurst, QA; Nieto, JML; Corma, A; (1998) Paramagnetic-superparamagnetic transition in molecular-sieve-supported antiferromagnetic particles. IEEE TRANSACTIONS ON MAGNETICS , 34 (4) 1030 - 1032.

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Abstract

Molecular sieves of the type CoAPO-5 have been studied by TEM and ac susceptibility measurements. In the as-synthesised state the material is paramagnetic due to the isolated cobalt ions and microstructurally it looks very homogeneous. After calcination the system develops very small cobalt-containing particles of a size between 1 and 3 nm, is paramagnetic at high temperature, superparamagnetic below about 20 K and starts to experience particle blocking below about 5 K. The tendency of cobalt to produce oxides and hydroxides of antiferromagnetic nature, together with the observed reduction of the effective moment below 20 K suggests that this is indeed a paramagnetic-superparamagnetic transition of antiferromagnetic particles. The susceptibility data have been used to estimate the degree of intraparticle spin uncompensation.

Type: Article
Title: Paramagnetic-superparamagnetic transition in molecular-sieve-supported antiferromagnetic particles
Location: SAN FRANCISCO, CALIFORNIA
Keywords: ac susceptibility, antiferromagnetic particles, superparamagnetism, COBALT
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
URI: http://discovery.ucl.ac.uk/id/eprint/59483
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