Abstract
Recent studies on nanosized near half-doped manganites reported that the charge-ordered antiferromagnetic states present in their bulk counterparts are strongly suppressed and that ferromagnetic behaviors appear at low temperatures as the particle size is reduced to nanometer scale. In this paper, the effects of size reduction on the magnetic properties of Sm0.5Sr0.5MnO3, which shows a sharp first-order ferromagnetic transition and an inhomogeneous phase dominated by a charge-ordered antiferromagnetic state above TC in the bulk form, have been investigated. The Sm0.5Sr0.5MnO3 nanoparticles of ∼40 nm were prepared by a sol−gel method, and their magnetic properties were studied by magnetometry. It is found that similar suppression of the charge-ordered antiferromagnetic state by size reduction is also present in this system. Most interestingly, two novel phenomena associated with this suppression are observed in the nanoparticles. One is that the inhomogeneous phase above TC is dominated by the ferromagnetic interactions in place of the antiferromagnetic ones and can be well described as a Griffiths phase. The other is that the nature of the ferromagnetic transition changes from first-order to second-order. These results may provide a deeper insight into the physics of the effects of size reduction on the half-doped manganites.
Published Version
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