Abstract

The structural, magnetic and vibrational properties of the BaMn_1-xTi_xO₃ system (0 ≤ x ≤ 0.25) have been studied by X-ray and neutron powder diffraction, electron spin resonance (ESR) and Raman spectroscopy methods. A sequence of the structural phase transitions 15R → 8H → 9R → 10H → 12R was observed upon Ti doping. The structural parameters of the observed phases were determined. Antiferromagnetic ordering in the 15R, 9R and 8H structural phases was observed at low temperatures. The magnetic propagation vector is q = (0 0 1/2) for the 15R and 9R phases and q = (0 0 0) for the 8H phase. The magnetic ordering temperatures and the ordered Mn magnetic moments are suppressed rapidly with increase of the Ti concentration from T_N = 230 (x = 0) to 100 K (x = 0.25) and m = 2.0 to 1.2 μ_B, respectively. The relationship between the Raman spectra of different structural phases of BaMn_1-xTi_xO₃ and concentration dependencies of the vibrational modes were analyzed.