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arXiv · 1311.0240

Magnetism in nanoparticle LaCoO3

A. M. Durand·D. P. Belanger·F. Ye·S. Chi·J. A. Fernandez-Baca·C. H. Booth·M. Bhat
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Abstract

LaCoO3 (LCO) nanoparticles were synthesized and their magnetic and structural properties were examined using SQUID magnetometery and neutron diffraction. The nanoparticles exhibit ferromagnetic long-range order beginning at T_C approximately 87K that persists to low temperatures. This behavior is contrasted with the ferromagnetism of bulk LCO, which also starts at T_C approximately 87K but is suppressed below a second transition at T_o approximately 37K, due to a structural phase transition. The ferromagnetism in both systems is attributed to the tensile stress from particle surfaces and impurity phase interfaces. This stress locally increases the Co-O-Co bond angle gamma, and competes with the thermal contraction of the lattice. It has recently been shown that LCO loses long-range ferromagnetic order when gamma decreases below the critical value gamma_c = 162.8 degrees. Consistent with this model, we show that gamma in nanoparticles remains larger than gamma_c at low temperatures, likely a consequence of all spins being in close proximity to surfaces or interfaces.

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A. M. Durand, D. P. Belanger, F. Ye, S. Chi, J. A. Fernandez-Baca, C. H. Booth, M. Bhat. 2013-11-01. Magnetism in nanoparticle LaCoO3. https://arxiv.org/abs/1311.0240

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