Spin-glass-like properties of La0.8Ca0.2 MnO 3 nanoparticles ensembles

V. Markovich, I. Fita, A. Wisniewski, G. Jung, D. Mogilyansky, R. Puzniak, L. Titelman, G. Gorodetsky

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Abstract

Magnetic properties of compacted La0.8Ca0.2 MnO 3 manganite nanoparticles with average particle size of 18 and 70 nm and Curie temperatures TC 231 K and TC 261 K, respectively, have been investigated. The relative volume of the ferromagnetic phase has been estimated to be 52% for ensembles of 18 nm particles and 92% for 70 nm particles. It was found that applied hydrostatic pressure enhances TC of La0.8Ca 0.2 MnO3 nanoparticles at a rate d TC /dP1.8-1.9 K/kbar, independently on the average particle size. Pronounced irreversibility of magnetization below Tirr 208 K and strong frequency dependent ac susceptibility below TC for smaller 18 nm particles have been observed. 18 nm particles have also shown aging and memory effects in zero-field-cooled (ZFC) and field-cooled magnetization. These features indicate the appearance of spin-glass-like state, partially reminiscent the behavior of La1-x Cax MnO 3 crystals, doped below the percolation threshold x< xC =0.225. In contrast, ensembles of larger 70 nm particles have shown insignificant irreversibility of magnetization only and no frequency dependence of ac susceptibility, similarly to the behavior of La1-x Cax MnO3crystals with x> xC. The temperature of the ZFC magnetization maximum for 18 nm particles decreases with increasing magnetic field and forms a critical line with an exponent 1.89±0.56. The results suggest that superspin-glass features in ensembles of interacting 18 nm particles appear along with superferromagnetic-like features.

Original languageEnglish
Article number134440
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume81
Issue number13
DOIs
StatePublished - 30 Apr 2010

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