Crystal structure and magnetic properties of the BaFe12−xAlxO19 (x=0.1–1.2) solid solutions

• Structure and magnetic properties for BaFe12−xAlxO19 (x=0.1–1.2) are investigated.
• Atomic coordinates and lattice parameters are Rietveld refined.
• Invar effect is observed below150 K.
• Increase of microstress value with decreasing temperature is defined.
• Curie temperature and total magnetic moment per formula unit are defined.

The investigations of the crystal and magnetic structure by powder neutron diffractometry as well as the magnetic properties by vibration sample magnetometry for the BaFe12−xAlxO19 (x=0.1–1.2) solid solutions have been performed at different temperatures and magnetic fields. The atomic coordinates and lattice parameters have been Rietveld refined. The Invar effect has been observed in low temperature range (from 150 to 4.2 K). It was explained by the thermal oscillation anharmonicity of atoms. The increase of microstress value with decreasing temperature has been defined from Rietveld refinement. The Curie temperature and change of total magnetic moment per formula unit have been defined for all the compositions of the barium hexaferrites BaFe12−xAlxO19 (x=0.1–1.2) solid solutions. The magnetic structure model is proposed. The most likely reasons and the mechanism of magnetic structure formation are discussed.