Superparamagnetic behaviour and deviation from Bloch T^3/2 law of La_0.7Ca_0.3MnO₃ nanoparticles
by Do Hung Manh; Tran Dang Thanh; Nguyen Van Chien; Vu Dinh Lam; Le Van Hong; Nguyen Xuan Phuc; Pham Thanh Phong
International Journal of Nanotechnology (IJNT), Vol. 10, No. 3/4, 2013

Abstract: In this study, we investigated superparamagnetism behaviour and saturation magnetisation of single-phase, nanocrystalline, granular La_0.7Ca_0.3MnO₃ (LCMO) samples synthesised by reactive milling method. The superparamagnetic behaviour of as-milled samples with various milling times was studied in the temperature range from 200 K to 300 K. The saturation magnetisation of the samples increased from 14.7 to 36.8 emu/g with higher values corresponding to shorter milling time. The observed un-overlapping of the scaled M(H_ext, T)/M_S versus H_ext/T plots and the Curie-Weiss like behaviour of the dc-susceptibility at high temperatures provide evidence that the nanoparticles are interacting superparamagnetic ensembles. The magnetisation curves of interacting nanoparticles were well described by the argument-corrected Langevin function. The saturation magnetisation versus temperature showed a T^ε dependence with ε deviated from 3/2 (value for the Bloch law), which increased with decreasing of the milling time.

Online publication date: Fri, 05-Apr-2013

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