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Influence of Simultaneous Doping of Li^+ and Fe^{3+} Ions in the LiMn_2O_4 Spinel Structure

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Nowicki W.

Acta Physica Polonica A

2008

vol. 114

issue 2

375-382

A series of compounds Li_xMn_{3-x-y}Fe_yO_4 (x=1.0125;0≤y≤0.05) were synthesized by solid state reaction of Li_2CO_3 with the manganese oxide or iron-manganese oxide precursors. Investigations of the structure transformation effect of double substitution with Li^+ and Fe^{3+} ions in LiMn_2O_4, in the temperature range of 10-300 K, were undertaken using high-resolution X-ray powder diffraction at the HASYLAB (DESY) synchrotron. The Li_{1.0125}Mn_{1.9625}Fe_{0.025}O_4 transforms from cubic (Fd3̅ m) to orthorhombic (Fddd) below 250 K, and is stable to 10 K. Whereas in the Li_{1.0125}Mn_{1.9375}Fe_{0.05}O_4 oxide no phase transition was observed, this spinel remains in cubic structure down to the temperature of 10 K.

Magnetic Stripes on Hexagonal Lattice with Competing Exchange and Dipole-Dipole Interactions

100%

Joknys A., Tornau E.

Acta Physica Polonica A

2008

vol. 113

issue 3

951-954

We obtained the phase diagram for the Ising model with competing exchange and dipolar interactions on 2D hexagonal lattice. By using histogram method we determined the order of the phase transition from isotropic stripe phase to low-temperature anisotropic stripe phases AFh of different stripe widths h. The first order phase transition was found to AF1 and AF2 phases and the second order - to AF3 and AF4 phases. We have also found that in AF1 phase stripe domain grows with time as t^{0.5}. In phases AF3 and AF4 stripe domain growth is proportional to log t.

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2 Acta Physica Polonica A

2 2008

1 Joknys A.

1 Nowicki W.

1 Tornau E.

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Influence of Simultaneous Doping of Li^+ and Fe^{3+} Ions in the LiMn_2O_4 Spinel Structure

Magnetic Stripes on Hexagonal Lattice with Competing Exchange and Dipole-Dipole Interactions