Deviation from Bloch’s T3/2 Law and Spin-Glass-Like Behavior in La0.7Ca0.3MnO3 Nanoparticles

Abstract

Three samples of La 0.7 Ca 0.3 MnO 3 nanoparticles were prepared by a reactive milling method with the milling times t m = 8, 12, and 16 h. The studies based on X-ray diffraction and electron microscopes reveal that the mean particle size of nanoparticles is about 7 nm. Saturation magnetization values determined from fitting the Langevin function to the magnetization curve at 5 K decrease from 36.8 to 14.7 emu/g with increasing t m from 8 to 16 h. Particularly, temperature dependences of saturation magnetization for these samples do not follow Bloch's T 3/2 law, but follow a T ε law. The results obtained from investigating the DC magnetization and AC susceptibility indicate an existence of the spin-glass-like behavior in the samples, which is ascribed to the competition of ferromagnetic and anti-ferromagnetic interactions.

Electrical and magnetic properties of La0.7Ca0.3MnO3 nanoparticle prepared by reactive milling method

“…In the first step, the precursors were mixed and milled at an agitation speed of 875 rpm for 8 h in ambient atmosphere. The obtained product was LCMO-NP with the particle size of about 15 nm, whereas the crystal size (<D>) of about 8 nm [17,26]. In the second step, this powdered product was pressed into tablets under a pressure of 5000 kg cm −2 , and then annealed at 900 °C for 1 h in air.…”