Magnetic properties of nanocomposite manganites p-La0.78Mn0.99O3.5 and p-La0.8Mn1.04O3.5

Anna I. Rykova 1Eugene N. Khatsko 1Alexander S. Cherny 1Victor N. Uvarov 2Tatyuna E. Konstantinova 3

1. Institute for Low Temperature Physics, 47 Lenin ave., Kharkov 61103, Ukraine
2. Institute for Metal Physics, N.A.S.U., 36 Vernadsky Boulevard, Kyiv 03142, Ukraine
3. Donetsk Institute for Physics and Engineering, NASU, Donetsk 83114, Ukraine


En experimental investigations of the structure and magnetic properties of nanocomposite manganites p-La0.78Mn0.99O3.5 and p-La0.8Mn1.04O3.5 are presented. The semiconducting composite nanomaterials р-La0.78Mn0.99O3,5 and р-La0.80Mn1.04O3.5 р-type of conduction was produced by high pressure technique at 7.5 GPa.

The X-ray diffraction measurements show, that samples are single-phase with the cubic perovskite crystal structure and with unit cell parameters: a = 3.860 ± 0. 003 Ǻ, for p-La0,78Mn0,99O3,5 sample and a = 3.8762 ± 0, 0051 Ǻ, for р-La0.80Mn.,04O3.5. The nanostructure of these manganites were investigated by scanning atom-force microscopy method. The most characteristic value of nanograins diameter is near 70 nm.
The temperature dependence of magnetic susceptibility in temperature range 4.2 – 300 K for both samples was studied in small external magnetic field 25 Oe. There is clear-cut distinguishes between samples with different composition and thermal annealing. At temperature near 260 K for both specimens there are anomalies typical for the phase transition to a ferromagnetically ordered state. At temperatures above Tc the susceptibility behaviors are described by Curie-Weiss law quite well. But the difference in the curves of the temperature dependence of magnetic susceptibility in ZFC and FC regimes argues for phase separation and spin cluster phase existence.
The magnetization curves M(H) in the wide range of temperatures from 4.2 up to 260 K was also measured. They demonstrate typical for ferromagnets behavior with temperature depended hysteresis. The temperature dependence of saturation moment are different for both samples, nevertheless both of them can be described with Brillouin function.

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Anna I. Rykova
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-11 18:24
Revised:   2009-06-07 00:44
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