Magnetic properties of nanocrystalline La1-xMnO3+delta manganites: size effects

作者：Markovich V^*; Fita I; Mogilyansky D; Wisniewski A; Puzniak R; Titelman L; Vradman L; Herskowitz M; Gorodetsky G

来源：Journal of Physics: Condensed Matter , 2007, 19(34): 346210.

DOI：10.1088/0953-8984/19/34/346210

The magnetic properties of nanocrystalline manganites La1-xMnO3+delta with particle size of 20 (LMO20), 25 (LMO25), and 30 nm (LMO30), prepared by the citrate method, have been investigated in the temperature range 5 320 K, magnetic field up to 90 kOe and under quasi- hydrostatic pressures up to 14.5 kbar. The studies involve sequential zero- field- cooled magnetization (M) measurements followed by magnetization measurements during cooling in the same magnetic field (H) and complementary measurements of ac susceptibility. Additional measurements of M versus H were carried out at ambient and applied pressures. All nanoparticles exhibit a paramagnetic to ferromagnetic transition (PFT) at a Curie temperature T-C > 200 K. It was found that the relative volume of the ferromagnetic phase increases for larger particle size and approaches a value of about 93% for LMO30. The real part of the ac susceptibility of sample LMO20 exhibits strong frequency dependence in a wide temperature range below TC, whereas for sample LMO30 only relatively weak frequency dependence was observed. The magnetization of sample LMO30 exhibits a PFT of second order; the type of transition could not be established for the smaller particles. It was found that an applied pressure enhances the TC of La1-xMnO3+delta nanoparticles with a pressure coefficie

• 出版日期2007-8-29