Int. J. Nanotechnology, Vol. 10, Nos. 3/4, 2013 197 Copyright © 2013 Inderscience Enterprises Ltd. Superparamagnetic behaviour and deviation from Bloch T 3/2 law of La 0.7 Ca 0.3 MnO 3 nanoparticles Do Hung Manh*, Tran Dang Thanh, Nguyen Van Chien, Vu Dinh Lam, Le Van Hong and Nguyen Xuan Phuc Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay Distr., Hanoi, Vietnam Email: manhdh@ims.vast.ac.vn Email: thanhtd@ims.vast.ac.vn Email: chienft.u@gmail.com Email: lamvd@ims.vast.ac.vn Email: honglv@ims.vast.ac.vn Email: phucnx@ims.vast.ac.vn *Corresponding author Pham Thanh Phong Nha Trang Pedagogic College, 01 Nguyen Chanh Street, Nha Trang City, Khanh Hoa Province, Vietnam Email: ptphong.nh@khanhhoa.edu.vn Abstract: In this study, we investigated superparamagnetism behaviour and saturation magnetisation of single-phase, nanocrystalline, granular La 0.7 Ca 0.3 MnO 3 (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. Keywords: perovskite; reactive milling; particle size; nanoparticles; Curie- Weiss like behaviour. Reference to this paper should be made as follows: Manh, D.H., Thanh, T.D., Chien, N.V., Lam, V.D., Hong, L.V., Phuc, N.X. and Phong, P.T. (2013) ‘Superparamagnetic behaviour and deviation from Bloch T 3/2 law of La 0.7 Ca 0.3 MnO 3 nanoparticles’, Int. J. Nanotechnology, Vol. 10, Nos. 3/4, pp.197–205.