Physico-Chemical nanomaterials science 

Yttrium Iron Garnets Doped with Mn3+ and Al3+ions
Davydenko N.V., Yanchevskii O.Z., V’yunov O.I.
Solid State Chemistry Department, Vernadsky Institute of General 
and Inorganic Chemistry, National Academy of Sciences of Ukraine, 
Palladina ave., 32/34, Kiev-03142, Ukraine.
E-mail: nata.dvict@gmail.com

Yttrium iron garnet, Y3Fe5O12 has low dielectric losses, thermal stability, narrow line of ferromagnetic resonance, and due to these high characteristics is widely used in radio devices and satellite communication systems. Partial substitutions of Y3Fe5O12 cations for Al3+ and Mn3+ are promising for improving the magnetic and resonance characteristics of samples.
The complex garnets Y3Fe5-x‑yMnxAlуO12 with partial substitution of Fe3+ ions for Al3+ and Mn3+ ions was precipitated from aqueous solution. For all Al3+ contents (y = 0.60, 0.65, 0.70), the dependence of unit cell volume of samples depending on manganese content pass through a minimum at x = 0.15 (Fig. 1). It can be assumed that at low manganese content (0 < x ≤ 0.15), high-spin (HS) Fe3+ ions (RFe3+ = 0.645Å) are preferably substituted for low-spin (LS) Mn3+ ions with lower ionic radius (RMn3+ = 0.580 Å), and unit cell volume decreases.	
Fig. 1. Unit cell parameters of Y3Fe5-х-уMnxAlуO12	
At higher manganese content (0.15<x≤0.20), Fe3+ ions are substituted for Mn2+ ions with higher ionic radius (RMn2+ = 0.670Å (LS) and 0.830Å (MS)), and unit cell volume increases.
In comparison with Y3Fe5O12 ceramic, Y3Fe5-х-уMnxAlуO12 ceramic at x = 0.15 have lower saturation magnetization and higher sensitivity to the magnetic field. At x + y ≥ 0.8, the dielectric losses decrease to tg de = 1.8·10-4 in the range 10 12.5 GHz. Therefore, the materials investigated are promising as high-Q resonance elements.

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